Abstract: Transcranial direct current stimulation (tDCS) as a non-invasive form of neuromodulation, has found widespread application in enhancing cognitive abilities and treating psychiatric disorders and neurological diseases. However, its clinical translation remains hindered by challenges such as inconsistent parameter selection and insufficient standardization of protocols, which may stem from an incomplete understanding of its underlying mechanisms and the absence of widely accepted guidelines. This article aimed to systematically review and analyze existing research on tDCS, elucidated its mechanisms of action, and explored its potential for scientifically grounded applications in the treatment of various diseases such as autism spectrum disorders, chronic headaches (including migraines), refractory epilepsy, post-stroke rehabilitation, mental disorders, and Alzheimer's disease,compared transcranial direct current stimulation with transcranial alternating current stimulation,in order to provide a theoretical foundation and practical reference for future investigations.