The present study aims to investigate the role of vocabulary knowledge in composition writing among Chinese children. Drawing on Nation’s (2001) vocabulary framework, this study operationalized Chinese vocabulary knowledge from receptive and productive perspectives and in form, meaning, and use domain, respectively. A total of five measures assessing receptive vocabulary knowledge, productive vocabulary knowledge (form, meaning, and use), and composition writing skills were administered to 249 Chinese students in grade 4 (N = 91), grade 5 (N = 90), and grade 6 (N = 68). Hierarchical regression results showed that across upper elementary grades, productive vocabulary knowledge made a significant and substantial contribution to Chinese writing performance after controlling for age and receptive vocabulary knowledge. Inspections on vocabulary knowledge in each individual domain further revealed that knowledge of vocabulary form was the strongest predictor of writing performance at grade 4, while knowledge of vocabulary meaning and use make increasing contributions to composition writing at higher grades. Findings from this study underline the relative importance of productive vocabulary knowledge in form, meaning, and use at different developmental stages and extend writing models to non-alphabetical languages. Pedagogical implications were also drawn from the present study to inform better educational practices on scaffolding beginning writers with specific aspects of vocabulary knowledge.