Step 1. Switch off the mobile phone.
Step2. Press Volume UP+Power button and when mi Logo shown than release power button.
Step 3. Select Recovery Mode and connect the mobile phone to PC.
Step 4. Download MI Password Remover
Step 5. Unzip this file and Run Mi Reset.bat command in this folder. And Follow the instruction.
Step 6. After completion of this command , RUN adb.exe reboot command on command prompt.
Wait for reboot the mobile phone.