Hi, Changing Job

I have been working in Eastern china as Software engineer, city-Wuxi for about 3 years, right now i have new working permit with Type C category. so can any-one please enlighten me about procedure related to changing a new job in same city, as well as do i need to apply for a new working permit or just transfer it to another new employer. Is there any chance if i apply for a new working permit i can be denied.