when i use android phone connect Arduino 101‘s Ble ，it printed
Connected to central: ec:82:20:7f:dc:52
Battery Level % is now: 97
Battery Level % is now: 83
Battery Level % is now: 73
Battery Level % is now: 67
Battery Level % is now: 63
Battery Level % is now: 62
Battery Level % is now: 60
Battery Level % is now: 59
Battery Level % is now: 58
Battery Level % is now: 59
Battery Level % is now: 58
Battery Level % is now: 59
Battery Level % is now: 58
Battery Level % is now: 59
Battery Level % is now: 58
Battery Level % is now: 59
Disconnected from central: ec:82:20:7f:dc:52
What app are you using to connect to the 101?
I suggest the Nordic Master Control Panel app as a debug tool / sanity checker, even if you need your sketch to work with another app.
If the Nordic app does not give any disconnection problems then the original app you were using is at fault.