I'm Vietnamese. I 'll planning to visit Xinjiang this September, i ll visit Urumqi, Kanas, Turpan and some other cities. Do i need to ask for Xinjiang permit ?

No, you don't need a permit for your travel in these places.

hi there :
first i warmly welcome to xinjiang which is my home town .
if you have chines visa you don,t need any permit for to xinjiang .
I hihgly recommed to you turpan, kanas lake , kuqa , hotan , and kashgar .
urimqi already become chines city nothing to see up there .

more info all around xinjiang you most welcome .