Visual-motor integration (VMI) is crucial for children's literacy development, especially in writing Chinese characters, which are more complex than alphabetic letters. The developmental trajectory of VMI and its relationship with handwriting skills across different elementary school grades remain underexplored. This study investigates the developmental trajectory of VMI in Chinese primary school students across different grades and examines whether grade level moderates the relationship between VMI and handwriting ability. A total of 672 native Chinese students from grades 1 to 6 in Shandong and Henan Provinces, China, were assessed (330 females, M[subscript age] = 9.23 years). VMI was evaluated using the Beery Visual-Motor Integration Development Test. Handwriting fluency and accuracy were measured through the Digit and Character Writing Task, as well as the Paper-Pen Copying Task. VMI levels increased significantly from grades 1 to 3, then plateaued by grade 4. Grade level positively moderated the relationship between VMI and handwriting fluency, but negatively moderated the relationship between VMI and handwriting accuracy. VMI levels in Chinese primary school students show rapid early growth, followed by slower progression. VMI has a stronger influence on handwriting fluency in the upper grades, while it affects handwriting accuracy more in the lower grades. These findings underscore the variability in VMI development and offer valuable insights for targeted interventions.