The rapid development of China's 5G 'Internet Plus' industry has led to increasing use of the Internet to provide healthcare services. Internet-based services in China are already widely used to prevent, identify, monitor, and manage mental disorders, but few of these services have been formally evaluated. To provide a clear baseline of this rapidly evolving field, we searched articles published before December 31, 2022, about internet-based interventions and surveys for mental health-related conditions in China in five international databases (Web of Science, PubMed, PsycINFO, Embase, and Cochrane Library) and four Chinese databases (CNKI, SinoMed, VIP, and WanFang). The 143 identified studies-54 in Chinese and 89 in English-described internet-based interventions and surveys in individuals with mental disorders, community residents, college students, older adults, pregnant women, and health professionals. The number of identified studies, which were mainly conducted in economically developed regions of the country, quadrupled after the 2019 onset of the COVID-19 pandemic. Available studies suggest-but do not prove-that internet-based interventions can reduce the severity of psychiatric symptoms, decrease healthcare costs, and improve the quality of life for individuals with mental disorders. Innovative smartphone applications could potentially improve the quality and expand the scope of internet-based interventions, making them a key component in ongoing efforts to prevent and monitor mental illness, enhance the self-management of mental disorders, and alleviate psychological distress among adolescents and other at-risk populations. However, achieving this long-term goal will require establishing standardised methods of administering internet-based interventions, training mental health professionals to implement and monitor the interventions, identifying methods of maintaining the confidentiality of collected information, and rigorously assessing the effectiveness of the interventions based on periodic assessment of uniform outcome measures. Clinical and policy research about expanding internet-based mental health interventions should focus on confidentiality, efficacy, and cost-effectiveness.