Abstract: Objective This study analyzes the disease burden of Attention-Deficit Hyperactivity Disorder (ADHD) in children and adolescents in China and globally from 1990 to 2021, providing data support and strategic recommendations for public health policy and disease intervention. Methods Data on the incidence, prevalence, and disability-adjusted life years (DALYs) of ADHD in children and adolescents from 1990 to 2021 were obtained from the Global Burden of Disease (GBD) 2021 database. Joinpoint regression models were used to analyze the annual percentage change in disease burden, and socio-demographic index (SDI) was incorporated to analyze health inequality and frontier trends. Results From 1990 to 2021, the age-standardized incidence rate (ASIR), age-standardized prevalence rate (ASPR), and age-standardized DALYs rate (ASDR) for ADHD in China showed an upward trend, while they declined globally. China's ASIR increased from 280.61/100,000 to 356.80/100,000, ASPR rose from 3079.72/100,000 to 3653.25/100,000, and ASDR went up from 37.85/100,000 to 45.00/100,000. Globally, ASIR declined from 166.40/100,000 to 59.93/100,000, ASPR decreased from 1900.79/100,000 to 1730.67/100,000, and ASDR dropped from 23.28/100,000 to 21.22/100,000. ADHD disease burden was highest among the 5–14-year-old population, with males significantly higher than females. SDI showed a positive correlation with ADHD disease burden, and inequality among different socio-economic groups has somewhat alleviated, though there remains room for improvement in some countries. Conclusions The increasing ADHD disease burden in China contrasts with the global trend, highlighting the need for enhanced early screening interventions and age- and gender-sensitive strategies. High SDI countries should also focus on the impact of social and psychological factors, optimize diagnostic and treatment pathways, and promote health equity.