Objective: To explore the associations of moderate to vigorous intensity physical activity (MVPA) and sedentary behavior (SB) among primary and secondary school students and their parents, so as to provide a scientific basis for formulating targeted physical activity promotion strategies for children and adolescents. Methods: From 2021 to 2022, basic information and 24 h movement behaviors of 2 484 pairs of students and their parents were collected from five primary and secondary schools in Haizhu District, Guangzhou City, with a convenient sampling combining with cluster sampling method. Component regression models were constructed to analyze the relationship between parental MVPA, SB and primary and secondary school students MVPA and SB, and a component isochronous substitution model was used to explore the effects of mutual substitution between parental MVPA, residual components (time use components other than SB during the 24 h period), and SB on the behavioral activities of MVPA and SB in primary and secondary school students. Results: Parental MVPA and SB of students in grade 1 to 3 were positively correlated with both students MVPA and SB ( β=0.06, 0.12, P <0.01). The component isochronous substitution model showed that substituting 10 and 20 minutes of MVPA for SB by parents in grade 1 to 3 was associated with an increase in MVPA of students, and substituting 10 and 20 minutes of residual ingredients for SB was associated with a decrease in SB of students, with mean changes of 0.8 (95% CI =0.4-1.2) and 1.4 (95% CI =0.7-2.2) and -1.4 (95% CI =-1.7 to -1.1) and -2.9 (95% CI =-3.4 to -2.3)( P <0.05). No statistically significant associations were observed between parents of students in grades 4 to 6 and 7 to 9 and students physical activity and sedentary behaviour ( P >0.05). Conclusions Parents of students in grades 1 to 3 increases MVPA and decrease SB are beneficial to increase MVPA and decrease SB of students. Parents could promote physical activity among primary and secondary school students, and the intervention gateway should be advanced, with the low grades as the optimal intervention period.