Objective To observe the electromyography characteristics of children's handwriting with attention deficit hyperactivity disorder(ADHD),and explore its electrophysiological mechanism,so as to provide an objective basis for developing non-pharmacological treatment for such children.Methods Between September 2021 and April 2022,29 ADHD children were recruited from an ordinary public primary school and the psychiatric clinic of a class-3 grade-A hospital in Beijing.Among them,25 were boys and 4 were girls,with an average age of 8.21±1.78 years.Meanwhile,23 male and 5 fe-male healthy counterparts were selected with the age gap no more than 6 months.The Delsys wireless surface EMG system was used to collect the electromyographic signals of the abductor pollicis breve,the first dorsal interosseous muscle,the flexor radial carpi motor and the extensor finger muscles dur-ing their writing tasks such as tracing trajectories,writing Arabic numerals 0-9,26 small and capital English letters,Chinese characters one to ten and"Yong".The percentage of the averaged electromyog-raphy(AEMG)of a muscle in the sum value of all measured muscles,and the coefficient of differ-ence were selected to evaluate the muscle contribution rate and the consistency of exertion,respective-ly.Moreover,the independent sample t-test was employed to compare the two different groups with the significance set at α=0.05.Results There was a significant difference in the muscle contribution of abductor pollicis breve and first dorsal interosseous muscles when writing Arabic numerals and that of abductor pollicis breve muscles when writing Chinese characters between ADHD children(27.29%,25.58%and 27.53%)and their healthy counterparts(42.87%,19.96%and 37.13%)(P<0.05).Most muscle differentiation coefficients of ADHD children were higher than 100%,with that of the domi-nant hand radial wrist flexor muscle reaching 270%in the trajectory tracing task.Conclusion Accord-ing to the characteristics of EMG signals,school-age ADHD children show an immature writing pat-tern,including poor stability of writing-related muscles,insufficient control of small finger muscle groups,poor control of hand coordination,and insufficient muscle inhibition of non-dominant hand.It is recommended to conduct the electromyoelectric assessment of handwriting movements in ADHD chil-dren,so as to carry out targeted intervention at an early stage.