Welcome to the definitive guide about Root and Jailbreak of Xiaomi Mi Box
What you need:
1, Xiaomi Mi Box 3rd Generation (with firmware equal or greater than v1.3.50 - tested with v1.3.73)
2, A Pc (or VirtualMachine) running Windows 7/8/8.1
3, HDMI cable
4, USB to microUSB cable
5, USB Mouse (Wireless Mouse doesn't work)
6, TV/Monitor near the PC (with HDMI-in)
7, USB PenDrive (FAT32)
8, MicroSD (FAT32)