INTRODUCTION: Knee osteoarthritis represents the prevalent and incapacitating disease. Acupuncture, a widely used clinical treatment for knee osteoarthritis, has been shown to ameliorate pain and enhance joint function in affected individuals. However, there is a lack of evidence comparing different courses of acupuncture for knee osteoarthritis. In this trial, we will assess the effect of 4 weeks vs 8 weeks of acupuncture in patients with knee osteoarthritis. METHODS AND ANALYSIS: The protocol is a pragmatic, parallel, two-arm randomised controlled trial, with the data analyst and assessor being blinded. 148 eligible patients with knee osteoarthritis will be randomly allocated in a 1:1 ratio to receive 4-week or 8-week acupuncture. Electroacupuncture will be administered three times per week for 4 or 8 weeks, respectively. Patients with knee osteoarthritis in both groups will be followed up to 26 weeks. The primary outcome is the response rate at week 26, and secondary outcomes include knee joint pain, knee joint function, knee joint stiffness, quality of life, patient global assessment, the Osteoarthritis Research Society International response rate and rescue medicine. A cost-effectiveness analysis will be carried out over 26 weeks. ETHICS AND DISSEMINATION: The protocol has been approved by the Medical Ethical Committee of Beijing University of Chinese Medicine (2023BZYL0506). The study findings will be disseminated through presentation in a medical journal. Additionally, we plan to present them at selected conferences and scientific meetings. TRIAL REGISTRATION NUMBER: Chinese Clinical Trials Registry (ChiCTR2300073383; https://www.chictr.org.cn/showproj.html?proj=199310).