In case of divorce, the divorce certificate or the divorce judgment of the court is a valid proof of single.
Consult embassies and consulates in China, Vietnam for Vietnamese passport extension. Visa extension should be consulted with China Entry-Exit Administration.
In addition, regarding the visa issue: If Vietnamese and China people get married, they can apply for a visa to visit their relatives. After entering China, you can apply for a foreigner's residence permit and legally live and live in China. If you are divorced, you can no longer apply for a visitor visa. You can change other visas, such as tourist, business and work visas. However, if you have relatives with China nationality or permanent residence permit (commonly known as "green card"), such as children and parents, you can still apply for a visit visa.
If you are still in China, you can consult the Exit-Entry Administration of the local public security bureau in China about visa application.