Objective To explore the relationship between basic motor skills and social interaction ability in school-age children with moderate autism, and the mediating role of executive function and the realization path. Methods A cross-sectional design was used to investigate 117 school-age children with autism from Sep. to Dec. 2020. The level of basic motor skills was assessed by the test of gross motor development (TGMD), the impairment of executive function was assessed by the behavior rating inventory of executive function (BRIEF), and the social disorder was assessed by the social responsive scale-second edition (SRS-2). Pearson correlation analysis was used to explore the interrelationship, and structural equation modeling was applied to explore the path relationship. Results There was a significant negative correlation between the level of basic motor skills and SRS-2 scores (r＝－0.312, P＜0.001). There were significant negative correlations between the level of basic motor skills and the BRIEF scores of inhibition (r＝－0.336, P＜0.001), switching (r＝－0.325, P＜0.001), affective control (r＝－0.338, P＜0.001), task initiation (r＝－0.240, P＝0.009), working memory (r＝－0.278, P＝0.002), and planning (r＝－0.224, P＝0.015). The SRS-2 score was positively correlated with the BRIEF scores of inhibition (r＝0.378, P＜0.001), switching (r＝0.299, P＝0.001), affective control (r＝0.417, P＜0.001), task initiation (r＝0.246, P＝0.007), working memory (r＝0.409, P＜0.001), and monitoring (r＝0.258, P＝0.005). Executive function played a complete intermediary role between basic motor skills and social interaction ability (B＝－1.912, 95% confidence interval: －3.116 to －1.069). Conclusion In school-age children with moderate autism, executive function and social interaction ability change positively with the level of basic motor skills. Basic motor skills can affect social interaction ability through the mediating role of executive function, and inhibition and affective control are important pathways to achieve this.