BACKGROUND: The results of current population-based studies exploring the effects of prenatal phthalate exposure on children's behavioral problems are not completely consistent. In addition, it is not clear whether vitamins improve phthalate-induced health risks. METHODS: This study was based on the Ma'anshan Birth Cohort, which included 2910 mother-child pairs. To assess children's behavior, we used the Strengths and Difficulties Questionnaire (SDQ). A latent category growth model was used to model the scores of each subscale of the SDQ. Quantile g-computation and Bayesian kernel machine regression were applied to analyze the effect of prenatal cumulative phthalate exposure. RESULTS: Prenatal cumulative phthalate exposure was associated with the "borderline and abnormal emotional symptoms" trajectory (β = 0.146, 95 % CI = -0.0003, 0.292), affecting girls more in emotional areas, and boys in conduct areas. There was an interaction effect between folic acid supplementation, vitamin D levels and phthalate mixtures on the risk of abnormal emotional behavior in children, which was reflected mainly in prosocial behavior and conduct problems. CONCLUSIONS: Prenatal cumulative phthalate exposure increased the risk of abnormal emotional symptoms in children, and there were sex differences. The duration of folic acid supplementation and vitamin D level can affect the effects of cumulative phthalate exposure on emotion and behavior.