Background: Knee osteoarthritis (KOA) is a prevalent chronic degenerative disease, especially among athletes due to their high physical demands. While community-based Tai Chi is recommended for KOA rehabilitation, its feasibility is often limited by external factors like weather and logistics. Internet-based Tai Chi could offer a more accessible alternative. This study aims to compare the therapeutic effects of Internet-based Tai Chi with community-based Tai Chi in athletes with KOA and to explore the underlying mechanisms of Tai Chi's therapeutic action. Methods and Analysis: In this parallel randomized controlled trial, 96 athletes with KOA in China will be randomly assigned to either an Internet-based or a community-based Tai Chi group in a 1:1 ratio. The intervention consists of 60-minute Tai Chi sessions, conducted twice weekly for 12 weeks. Primary outcome measures include the Western Ontario and McMaster University Osteoarthritis Index. Secondary outcomes encompass the 20-meter walk test, Timed Up and Go test, Osteoarthritis Self-Efficacy Scale, SF-36 health survey, and assessments of muscle strength and ultrasound echo intensity in quadriceps, hip abductors, and core muscles, along with lateral trunk lean angle. Attendance rates and adverse events will also be documented. Assessments will occur at baseline, 3 months, and 6 months. Data will be analysed on both intention-to-treat and per protocol bases. Conclusion: This trial will provide insights into the viability and efficacy of Internet-based Tai Chi as a therapeutic option for athletes with KOA, comparing it against the traditional community-based approach. It will also contribute to the understanding of Tai Chi's therapeutic mechanisms in managing KOA, potentially offering an innovative, accessible rehabilitation strategy for athletes.