As mentioned in the question, when my macbook pro started Win7, the screen went black, as if it was shut down, but I could enter safe mode.
After several tossing, I found that it may be caused by the latest automatic update of Win7 (2018-4-10 and 2018-4-11 two updates (Windows Update)).
Repair method:
Restart, press F8 (fn+F8) key, after the startup menu appears, select the first item to fix the startup error, then select "Restore System" in the subsequent interface, and then select the restore point on 2018-4-6 to restore , an error will be reported later, don't worry about it, and it will be OK after restarting. I was scared later and quickly turned off the automatic update of windows Update.