Step 2: Click Download on the homepage of MIUI7 in official website, select the model and version of the mobile phone, download the MIUI7 system package in the history package, watch the tutorial, select the line brush method, download the brush tool miflash in the tutorial and install it on the computer, and downgrade the system line brush on the computer.
A degraded brush system may not work properly. If it doesn't work properly, you still need to upgrade your system.