The circumstances in which parents cannot act as guardians of their children include: (1) committing acts that seriously damage the physical and mental health of the ward; （2） Be negligent in performing the duties of guardianship, or fail to perform the duties of guardianship and refuse to entrust part or all of the duties of guardianship to others, causing the ward to be in a state of distress; （3） To commit other acts that seriously infringe upon the lawful rights and interests of the ward.
Legal basis:
Article 36 of the Civil Code of the People's Republic of China
Paragraph 1
If a guardian falls under any of the following circumstances, the people's court shall, upon the application of the individual or organization concerned, revoke his or her guardian status, arrange for necessary temporary guardianship measures, and appoint a guardian according to the principle that it is most beneficial to the ward:
（1） Conduct behaviors that seriously damage the physical and mental health of the ward;
（2） Be negligent in performing the duties of guardianship, or fail to perform the duties of guardianship and refuse to entrust part or all of the duties of guardianship to others, causing the ward to be in a state of distress;
（3） To commit other acts that seriously infringe upon the lawful rights and interests of the ward.
