Attention Deficit Hyperactivity Disorder (ADHD) has a prevalence of about 5% and may cause inferiority complex, personality disorders, interpersonal impediment, and even anti-social behaviors in affected children if not treated early. In the past, the diagnosis of ADHD patients mainly depended on paper tests or behavior scales. However, such tests are usually time-consuming and their application suffers from constraints of external conditions in terms of test content and test type. Through the application of VR technology including head mounted display(HMD), game technology and sensors, this study develops and constructs an interactive panoramic virtual classroom scenario in which a blackboard embedded with listening test, CPT test, executive test, and visual memory test specially designed for attention and executive functions is incorporated; moreover, this study also develops a new assessment & diagnosis system based on children's performance, behavior & reaction in the above-mentioned four tests through an enormous and systematic design of a battery of visual & auditory distractions of different intensity levels, durations, and sequence. The system developed in this study is used to carry out a pilot trial on healthy volunteers and its functionalities are confirmed by the test results.