Due to the use of Android studio with SDK23, but other versions of the SDK are not installed, these days due to the need to use the lower version of the SDK, so use the Android SDK Manager to update accordingly. The beginning of the time is always unable to download, the first thought is the wall. So
File-->settings-->appearance & Behavior-->system settings-->http proxy settings for the corresponding agent
When you are finished setting up, Check connection
At this point, it is common sense that the Android SDK Manager can download the installation package normally. But no matter how I try. Later, I looked at the tools-->options inside the SDK manager and found that there was a need for proxy settings for the SDK manager. So set a pass, look at the log again, and then stop.
Just wait for it to be installed, and you can use this time to do something else. ^_^...
Android Studio Online install Android SDK considerations