Huawei Mate 9 root for android oreo is now available and it has been tested by me. I have tested it on latest USA firmware B370. Before rooting be informed that you will lose warranty by rooting your device. You are also not advised not to perform OTA upgrade after root.

Rooting Guide (Super SU):

• Backup all important data from Phone to PC
• You need sd card with 50MB available storage
• Unlock bootloader of your tablet (How to unlock ?)
• Download SuperSU from THIS LINK
• Copy SuperSU zip file on your external sd card
• Download TWRP installer from THIS LINK  (source:xda)
• Connect phone is fastboot (Power off phone, hold volume down and insert cable, fastboot mode should start)
• Extract downloaded TWRP installer file, and open MAF32.exe
• Type ” fastboot flash recovery_ramdisk twrp_mate9.img ” and press enter
• Disconnect phone from computer, and hold volume up and power, keep holding until see TWRP  Screen.
• Swipe to allow modifications, tap on install and select storage (external storage) press ok
• Then select “SR5-SuperSU-v2.82-SR5-20171001224502.zip” and swipe to install
• Reboot phone
• Install root checker and verify root access.

Rooting Guide (Magisk):

• Backup all important data from Phone to PC
• You need sd card with 50MB available storage
• Unlock bootloader of your tablet (How to unlock ?)
• Download Magisk from THIS LINK
• Copy Magisk zip file on your external sd card
• Download TWRP installer from THIS LINK  (source:xda)
• Connect phone is fastboot (Power off phone, hold volume down and insert cable, fastboot mode should start)
• Extract downloaded TWRP installer file, and open MAF32.exe
• Type ” fastboot flash recovery_ramdisk twrp_mate9.img ” and press enter
• Disconnect phone from computer, and hold volume up and power, keep holding until see TWRP  Screen.
• Swipe to allow modifications, tap on install and select storage (external storage) press ok
• Then select “Magisk v16.0.zip” and swipe to install
• Reboot phone
• Install root checker and verify root access.

Video Tutorial