Probiotics are widely used as supplement for various neurodevelopmental disorders. The mechanism of their therapeutic potential lies in the gut-brain axis, a two-way communication pathway through the neuroendocrine system. In the past, there have been many experiments to study the possible efficacy of probiotics in patients with ADHD. Although some studies have shown that probiotics can improve ADHD symptoms, most studies have used behavioral rating scales to evaluate. As a result, it is susceptible to informant bias. Standardized attentional tests and quantitative electroencephalogram (qEEG) can provide more objective data and detect possible changes in brain networks. Such changes may precede behavioral phenotypes. Therefore, the purpose of this study is mainly to detect the therapeutic effect of multiple strains of probiotics in patients with attention deficit hyperactivity disorder by using standardized attention tests and quantified brain waves (qEEG).