The accelerated development of digital technology has brought new opportunities for the innovation of adolescent mental health service models. Through international case analysis, the paper finds that developed countries have established adolescent mental health service systems with significant digital-empowerment characteristics. For example, the Crisis Text Line of US realizes risk-graded responses by relying on language processing technology, the Kooth platform of UK develops an Artificial Intelligence (AI) counseling system using cognitive-behavioral therapy, ReachOut of Australia has established a digital mental health resource library, SPARX of New Zealand reshapes the treatment experience with a gamified interface, and "Annie Advisor" of Finland pioneers the application of affective computing technology. The above innovative practices present six characteristics: precision service supply based on big data, intervention systems integrated with artificial intelligence, anonymous mechanisms to ensure privacy and security, highly accessible services that break through time and space limitations, human-machine collaborative dual track support models, and interdisciplinary service systems, providing many references and implications for China to continuously and deeply explore digital technology-empowered youth mental health services.