Objective: To investigate parents acceptance to the COVID-19 vaccine booster shots for their children aged 3-11 years in Nanjing based on the theory of planned behavior, and to provide a scientific theoretical basis for carrying out COVID-19 booster vaccination among children of this age group. Methods: A total of 1 286 parents of children aged 3-11 years in Nanjing were selected by multistage stratified cluster sampling. A questionnaire survey based on the theory of planned behavior was used to investigate their willingness to vaccinate their children with the COVID-19 booster dose, and structural equation model was used to conduct data analysis. Results: About 90.2% of parents were willing to give their children a booster dose of the COVID-19 vaccine. The model constructed based on the theory of planned behavior could explain 42.2% of the variance of vaccination acceptance. Attitudes and perceived behavioral control had a direct positive effect on parents acceptance to booster dose of the COVID-19 vaccine (path coefficients were 0.47 and 0.18, P <0.01); The direct effect of subjective norms on vaccination acceptance was not statistically significant; Perceived behavioral control and subjective norms could have indirect positive effects on vaccination acceptance through attitudes (path coefficients were 0.27 and 0.13, P <0.01). Conclusion Parents in Nanjing have a higher acceptance to vaccinate their children aged 3-11 years with the COVID-19 vaccine booster dose. The theory of planned behavior shows a good explanatory ability on parents acceptance to vaccinate their children, and attitude plays an important role in the formation of vaccination acceptance.