A month ago, the usb ports besides SD card reader stop working for no reason. And Then the other one has the same issue few days ago. Now I can't use my wireless mouse and printer. I've tired to reset PRAM and SMC and that didn't change anything. Does anyone know the possible solution? by the way, my macbook pro is 2011 OX 10.6.8.
I would first run an Apple Hardware Test and see if you've any errors, as what you have is likely a hardware problem.
If errors or found (or even if they're not) you should take your machine to your local Apple Store or an AASP and have them run extensive hardware tests. Did you buy AppleCare with your 2011 model? If so, the repair shouldn't cost you a thing.