Huawei P9 Root for nougat is available. Lots of users requested to share a working root method for Huawei P9. You will be able to root your phone by following the guide given below. By rooting your phone you will lose warranty, as you are required to unlock bootloader of your phone.

Rooting Tutorial:

• Backup all important data from tablet to PC
• Unlock bootloader of your tablet (How to unlock ?)
• Download latest SuperSU from THIS LINK
• Copy SuperSU file on your sd card
• Download TWRP recovery from THIS LINK (Thanks to greatslon)
• Extract downloaded zip file, and connect phone in fastboot mode
• Open MAF32.exe and type ” fastboot flash recovery twrp_P9_5_greatslon.img ” then press enter
• Once recovery flashed, disconnect phone from pc, then hold volume+ and power, keep holding until you see TWRP screen.
• Swipe to allow modifications, if requested then tap on install, browse to sd card and install SuperSU file
• Reboot and verify your root access.

Source: XDA