Background: While socioeconomic status (SES) has been shown to be an important determinant of sedentary behaviour (SB) and moderate-to-vigorous intensity physical activity (MVPA) in typically developing children, similar data on those with intellectual disability (ID) are lacking. This study explored the association of SES with SB and MVPA among Chinese children with ID. Method: Data were collected from 275 children aged 7-16 with mild to severe ID. Children's Leisure Activities Study Survey assessed SB and MVPA for a week. SES was assessed using the six indicators. Multiple linear regression was used to analyse the associations of SES variables with SB and MVPA on schooldays and on weekends. Results: Parental education level was positively associated with SB on weekends, and MVPA on schooldays and weekends; family's combined annual income was positively associated MVPA on schooldays and weekends; parental occupation was positively associated with SB on schooldays and weekends; Family Affluence Scale was positively associated with SB on schooldays (all p < 0.05). Conclusion: SES plays a significant role in influencing SB and MVPA in children with ID. Results suggest that interventions should focus on increasing MVPA for children with lower SES, while families with higher SES should limit their children's SB.