Children and adolescents are highly susceptible to problematic smartphone usage. We employed network analysis to explore the similarities and differences in the core symptoms of problematic smartphone use across grades 4–9, using a large nationwide sample. This study included 8552 children and adolescents (Mage = 12.98, SD=1.51) who met the critical value for problematic smartphone use. The results showed that the core symptoms of problematic smartphone use exhibit both similarities and differences between grades 4 and 9. ’Withdrawal symptoms’ and ’preoccupation symptoms’ were the stable core symptoms of problematic smartphone use across grades 4 to 9, suggesting that problematic smartphone use begin to appear from earlier grades, such as grade 4. ’Feel impatient and fretful’, ’never give up’ and ’always thinking about’ were the core symptoms in grades 4 and 5. ’Longer than I had intended’ and ’hard to concentrate’ emerged as additional core symptoms in grade 6, with the intensity indicators peaking in grades 8 and 9, suggesting that the issue of problematic smartphone use among Chinese children and adolescents has become intensified and intricate. Symptoms of problematic smartphone use vary across grades and exhibit both continuity and stage specificity. Consequently, to address this issue, the formulation of intervention measures should comprehensively consider both the grade levels and symptoms.