due very unstable?

I bought a arduino due,
But this board is very unstable,
the serial port often disconnect from PC,
I must re-plug it to sub hub.

How this happens?

The programming port is super stable. The native USB port is a USB 2.0 On the Go High Speed (clocked at 480 MHz, OTG HS) and as soon as an electrical default is detected, it tries to change the COM port.

Maybe your USB cable is the issue, try another cable.