Resignation just after the probation period does not require a fine. According to the legislative intent of the Labor Contract Law, resignation is the legal right of workers. As long as the necessary notification obligations are fulfilled, you can leave your job at the expiration without the approval of the employer. Of course, there is no need to pay liquidated damages.

Labor Contract Law

Article 37 A laborer may terminate the labor contract by giving a written notice to the employing unit 30 days in advance. The employee may terminate the labor contract by notifying the employer three days in advance during the probation period.