Attention-deficit/hyperactivity disorder (ADHD) is often accompanied by executive function deficits and functional alterations in sensory integration. The present study aimed to investigate the relationship between ADHD core symptoms, executive function, and sensory integration in children with ADHD. A total of 228 children with ADHD were recruited for our study. The Sensory Organization Test (SOT) and Child Sensory Integration Scale (CSIS) evaluated the sensory integration ability from lab-based and scaled-based perspectives, respectively. Three core components of executive functions (inhibition, working memory, and set-shifting) were assessed using both lab-based tests and the relevant factors from the behavior rating inventory of executive function (BRIEF). Partial correlation analysis was performed to explore the correlation of sensory integration with EF and ADHD core symptoms. Based on the observed significant correlation, bootstrap analyses were further conducted to explore the potential mediating effect of EF on the relationship between sensory integration and ADHD core symptoms. ADHD symptoms and EF were significantly correlated with CSIS scores; no factors were significantly correlated with SOT performance. In detail, the vestibular-balance score was negatively correlated with both inattention and hyperactivity/impulsivity symptoms, while the hyper-sensory and proprioception scores were negatively correlated with only inattention symptoms. For the scaled-based EF, vestibular-balance was negatively correlated with inhibition and working memory, and the hyper-sensory score was negatively correlated with shift factor. No correlation was found for the lab-based EF tests. The subsequent mediation analysis found that inhibition partially mediated the relationship between vestibular balance and hyperactivity/impulsivity symptoms. Working memory completely mediated the relationship between vestibular-balance, hyper-sensory, proprioception, and inattention symptoms. These results were well validated in an independent sample. Our present findings demonstrated that the functional alteration in basic sensory integration might be associated with impairments of executive functions and then lead to the behavioral expression of ADHD. The present findings might provide a new perspective to understand the occurrence of ADHD symptoms and potential precise intervention methods.