以下地址都已不能下载了，放在这里主要为了研究 Max OS与XCode版本的对应关系。
如果想下载Xcode，可以在苹果网站上注册一个开发者帐号，只注册这个帐号是免费的。就可以从这里下载：
http://connect.apple.com/cgi-bin/WebObjects/MemberSite.woa/wa/downloads
要有帐号哦，登录后，点击右侧Downloads--》Developer Tools 进入列表，可以找到多个版本的下载。
最新版本，在最后面，可以直接看文章最后面。
iPhone SDK 2.2.1 Leopard (10.5.4)
http://developer.apple.com/iphone/download.action?path=/iphone/iphone_sdk_for_iphone_os_2.2.1__9m2621a__final/iphone_sdk_for_iphone_os_2.2.19m2621afinal.dmg
iPhone SDK 3.0 (Xcode 3.1.3) Leopard (10.5.7)
http://developer.apple.com/iphone/download.action?path=/iphone/iphone_sdk_3.0__final/iphone_sdk_3.0__leopard__9m2736__final.dmg
iPhone SDK 3.0 (Xcode 3.2) Snow Leopard (10.6.0)
http://developer.apple.com/iphone/download.action?path=/iphone/iphone_sdk_3.0__final/iphone_sdk_3.0__snow_leopard__final.dmg
iPhone SDK 3.1 with Xcode 3.1.4 Leopard (10.5.7)
http://developer.apple.com/iphone/download.action?path=/iphone/iphone_sdk_3.1__final/iphone_sdk_3.1_with_xcode_3.1_final__leopard__9m2809.dmg
iPhone SDK 3.1 with XCode 3.2.1 for Snow Leopard (10.6.0)
http://developer.apple.com/iphone/download.action?path=/iphone/iphone_sdk_3.1__final/iphone_sdk_3.1_with_xcode_3.2_final__snow_leopard__10a432.dmg
iPhone SDK 3.1.2 with XCode 3.1.4 for Leopard (10.5.7)
http://developer.apple.com/iphone/download.action?path=/iphone/iphone_sdk_3.1.2__final/iphone_sdk_3.1.2_with_xcode_3.1.4__leopard__9m2809.dmg
iPhone SDK 3.1.2 with XCode 3.2.1 for Snow Leopard (10.6.0)
http://developer.apple.com/iphone/download.action?path=/iphone/iphone_sdk_3.1.2__final/iphone_sdk_3.1.2_with_xcode_3.2.1__snow_leopard__10m2003.dmg
iPhone SDK 3.1.3 with XCode 3.1.4 for Leopard (10.5.7)
http://developer.apple.com/ios/download.action?path=/iphone/iphone_sdk_3.1.3__final/iphone_sdk_3.1.3_with_xcode_3.1.4__leopard__9m2809a.dmg
iPhone SDK 3.1.3 with XCode 3.2.1 for Snow Leopard (10.6.0)
http://developer.apple.com/ios/download.action?path=/iphone/iphone_sdk_3.1.3__final/iphone_sdk_3.1.3_with_xcode_3.2.1__snow_leopard__10m2003a.dmg
iPhone SDK 3.2 Final with Xcode 3.2.2 for Snow Leopard (10.6.0)
http://developer.apple.com/ios/download.action?path=/iphone/iphone_sdk_3.2__final/xcode_3.2.2_and_iphone_sdk_3.2_final.dmg
Xcode 3.2.3 and iPhone SDK 4 GM seed for Snow Leopard (10.6.2)
http://developer.apple.com/ios/download.action?path=/iphone/iphone_sdk_4_gm_seed/xcode_3.2.3_and_iphone_sdk_4_gm_seed.dmg
Xcode 3.2.3 and iPhone SDK 4 Final for Snow Leopard (10.6.2)
http://developer.apple.com/ios/download.action?path=/iphone/iphone_sdk_4__final/xcode_3.2.3_and_iphone_sdk_4__final.dmg
Xcode 3.2.3 and iOS SDK 4.0.1 for Snow Leopard (10.6.4)
http://developer.apple.com/ios/download.action?path=/ios/ios_sdk_4.0.1__final/xcode_3.2.3_and_ios_sdk_4.0.1.dmg
Xcode 3.2.3 and iOS SDK 4.0.2 for Snow Leopard (10.6.4)
http://developer.apple.com/ios/download.action?path=/ios/ios_sdk_4.0.2__final/xcode_3.2.3_and_ios_sdk_4.0.2.dmg
Xcode 3.2.4 and iOS SDK 4.1 for Snow Leopard (10.6.4)
http://developer.apple.com/ios/download.action?path=/ios/ios_sdk_4.1__final/xcode_3.2.4_and_ios_sdk_4.1.dmg
Xcode 3.2.5 and iOS SDK 4.2 GM for Snow Leopard (10.6.4)
http://developer.apple.com/ios/download.action?path=/ios/ios_sdk_4.2_gm_seed/xcode_3.2.5_and_ios_sdk_4.2_gm_seed.dmg
Xcode 3.2.5 and iOS SDK 4.2 for Snow Leopard (10.6.4)
http://developer.apple.com/ios/download.action?path=/ios/ios_sdk_4.2__final/xcode_3.2.5_and_ios_sdk_4.2_final.dmg
Xcode 3.2.6 and iOS SDK 4.3 GM Seed for Snow Leopard (10.6.6)
http://developer.apple.com/devcenter/download.action?path=/ios/ios_sdk_4.3_gm_seed/xcode_3.2.6_and_ios_sdk_4.3_gm_seed.dmg
Xcode 3.2.6 and iOS SDK 4.3 for Snow Leopard (10.6.6)
http://adcdownload.apple.com/Developer_Tools/xcode_3.2.6_and_ios_sdk_4.3__final/xcode_3.2.6_and_ios_sdk_4.3__final.dmg
Xcode 3.2.6 and iOS SDK 4.3.1 for Snow Leopard (10.6.6)
http://adcdownload.apple.com/Developer_Tools/xcode_3.2.6_and_ios_sdk_4.3__final/xcode_3.2.6_and_ios_sdk_4.3.dmg
Xcode 4 and iOS SDK 4.3 for Snow Leopard (10.6.6)
http://developer.apple.com/devcenter/download.action?path=/Developer_Tools/xcode_4_and_ios_sdk_4.3__final/xcode_4_and_ios_sdk_4.3__final.dmg
Xcode 4.0.1 and iOS SDK 4.3.1 for Snow Leopard (10.6.6)
http://developer.apple.com/devcenter/download.action?path=/Developer_Tools/xcode_4.0.1_and_ios_sdk_4.3/xcode_4.0.1_and_ios_sdk_4.3.dmg
Xcode 4.0.2 and iOS SDK 4.3.2 for Snow Leopard (10.6.6)
http://developer.apple.com/devcenter/download.action?path=/Developer_Tools/xcode_4.0.2_and_ios_sdk_4.3/xcode_4.0.2_and_ios_sdk_4.3.dmg
Xcode 4.1 SDK5.0 for Snow Leopard (10.6.7)
Xcode 4.1 SDK5.0 for Lion (10.7)
Xcode 4.1.1 SDK5.0 for Lion (10.7)
Xcode 4.2 and iOS SDK 5.0 for Snow Leopard (10.6.7)
https://developer.apple.com/devcenter/download.action?path=/Developer_Tools/xcode_4.2_with_ios_5_sdk/xcode_4.2_and_ios_5_sdk_for_snow_leopard.dmg
Xcode 4.2 and iOS SDK 5.0 for Lion (10.7)
http://developer.apple.com/devcenter/download.action?path=/Developer_Tools/xcode_4.2_with_ios_5_sdk/xcode_4.2_and_ios_5_sdk_for_lion.dmg
Xcode 4.2.1 and iOS SDK 5.0 for Lion (10.7)