Do not power the BT module

On the BT module, press the button switch (keep pressed, and at the same time power the BT module
The LED on the BT module should now flash on/off every 2 seconds
Can now release the button switch on the BT module

After entering AT mode, type 1 and hit send

This happend to me when I try connect PC across Arduino Nano to Bluetooth, so what I must do?

Please re-read your Original Post and consider whether it would be meaningful for someone who knows nothing about what you are trying to do?

I certainly can't understand it.