Objective: To explore the effects of grandparent involvement in parenting on health related behaviors among urban preschool children, so as to provide a basis for the development of interventions for unhealthy behaviors among preschool children with different parenting pattern. Methods: A total of 5 431 preschool children aged 3-6 years old in Xinbei District, Changzhou City, were selected by census method during January to October, 2022. General household characteristics and health related behaviors of children were investigated by questionnaires, and the differences in health related behaviors with different parenting pattern involving grandparents were explored by the χ 2 test. A multifactorial Logistic regression model was used to analyze the effects of grandparenting on preschool children s health behaviors. Results: About 51.2% of preschoolers were raised by both parents, 46.1 % were co parented by grandparents, and 2.7% were raised by grandparents. After multifactorial Logistic regression analysis controlling for age, gender, annual household income, and family structure, children co parented by grandparents had a reduced risk of screen exposure time>1 h/d ( OR =0.79, P <0.05), with increased risks of outdoor activity time<2 h/d ( OR =1.30, P < 0.05 ), sleep duration <10 h/d ( OR =1.31, P <0.05), sleep difficulties ( OR =1.39, P <0.05) and adverse eating behaviors ( OR =1.20， P < 0.05), compared with children parented by both parents. Children raised by grandparents were at increased risk for outdoor activity time<2 h/d ( OR =2.19) and unhealthy eating behaviors ( OR =1.39) ( P <0.05). Conclusions Compared with children raised by both parents, the incidence of unhealthy behaviors is increased in children raised by parents and grandparents and in children raised by full grandparents. Active intervention should be focused on unhealthy behaviors of preschool children with pareting involving grandparents to promote the physical and mental health of preschool children.