I have built a dual system of Win8 and Win7. Now the boot interface is the 7 boot interface. How do I change it to the win8 boot interface?

First of all, we need to look at who controls the first boot interface.

I am not familiar with the boot settings of win8.

If you want to change the boot settings of win7 first and then switch to win8, you can switch to system32 in the system directory in the cmd of the win7 system and type:

bcdedit / ?

To modify the default boot settings.