It is not illegal to write unmarried when you are married. China's "Labor Law" and "Labor Contract Law" do not make this illegal. In the trial practice, only when the false personal information provided by employees seriously affects the company's judgment on its ability, and the rules and regulations clearly stipulate, the company can terminate the labor contract on this ground, such as forging academic qualifications, concealing that it has been subjected to criminal punishment, and concealing that it has signed a non-competition agreement with the original unit.

People's Republic of China (PRC) (China) Labor Contract Law

Article 26? The following labor contracts are invalid or partially invalid:

(1) Causing the other party to conclude or change a labor contract against its true meaning by means of fraud, coercion or taking advantage of the danger of others;

(2) The employer exempts itself from legal liability and excludes the rights of workers;

(3) Violating the mandatory provisions of laws and administrative regulations. Any dispute over the invalidity or partial invalidity of a labor contract shall be confirmed by the labor dispute arbitration institution or the people's court.