Can my employer cancel my visa and residence permit if I quit the job before the contract is over?

Yes, your former employer can cancel your visa in this case.

yes, so you should ask the previous employer for the dismissal letter and the working permit cancellation list. Then you can ask for another employer to extend your Z working visa. For more information, we can have a talk.

Foreign workers in China -

You should NEVER allow your employer to HOLD YOUR PASSPORT or FOREIGN EXPERTS CERTIFICATE. They are YOUR PERSONAL GOVERNMENT PAPERS and Chinese Law demands you, and YOU ALONE hold these documents. If an employer says otherwise, then they are lying and trying to control you, ILLEGALLY.

For US passport holders, The State Dept, says that you are to keep your passport securely on your person while abroad in case you are stopped, detained or in an accident. Furthermore it also reminds you that your passport is not YOURS! It belongs to the U.S. State Department.

Also The People's Republic of China Contract Labor Law, Article 9 states: When hiring an employee, the Employer shall not retain the employee’s resident
ID card or other documentation, nor demand the employee to provide security or collect property
from him/her under some other.

Help mine was canceled I was give. 30 days to live the country

Unfortunately there is generally no reprieve to this situation, and wrongful dismissal suits are generally not accepted by courts. If you fail to leave within the 30 days period it will be considered as overstay and may jeopardize your future chances of getting into the country.