Objectives Baduanjin is a Chinese form of low-intensity aerobic exercise that consists of eight movements. It is one of the most common forms of Chinese Qigong exercise, which originated during the Song dynasty and has a history of more than 1000 years. The aim of this research was to assess the efficacy of Baduanjin exercise for knee osteoarthritis (KOA). Methods A literature search was conducted of 10 databases (Web of Science, AMED, Scopus, CINAHL, MEDLINE, EMBASE, KoreaMed Synapse, Oriental Medicine Advanced Searching Integrated System, Chinese Wan Fang and China National Knowledge Infrastructure) from their inception to June 2019. We included eligible randomised controlled trials (RCTs) in which Baduanjin was employed either alone or as an adjuvant treatment for baseline interventions in patients with KOA. The Western Ontario and McMaster Universities Arthritis Index (WOMAC), Visual Analogue Scale (VAS) and response rate were used as important outcomes in this research. Risk of bias was assessed using the Cochrane Collaboration tool. Two reviewers independently selected studies, extracted data and assessed risk of bias. Meta-analysis was applied to quantitative data. Results Seven RCTs totalling 424 participants were included. Overall, only three studies (43 %) reported adequate random sequence generation, allocation concealment, blinding of outcome assessment and accounting for incomplete outcome data. The results showed a statistically significant mean difference (MD) between Baduanjin exercise and waiting list control on three domains of WOMAC scores [MD=-4.40 (95 % CI: -7.16, -1.64), p < 0.01 in pain; MD=-1.34 (95 % CI: -1.64, -1.04), p < 0.01 in stiffness; MD=-2.44 (95 % CI: -4.33,-0.55), p < 0.01 in physical function] and the response rate [RR = 1.18 (95 % CI: 1.01, 1.37), p = 0.04]. Moreover, when used alone, Baduanjin exercise demonstrated a statistically significant improvement on three domains of WOMAC scores [MD=-1.69 (95 % CI: -2.03, -1.35), p < 0.01 in pain; MD=-0.86 (95 % CI: -1.13, -0.58), p < 0.01 in stiffness; MD=-2.23 (95 % CI: -3.65,-0.82), p < 0.01 in physical function] compared to health education. Furthermore, Baduanjin exercise plus NSAID therapies significantly improved total WOMAC score [MD=-10.26 (95 % CI: -13.41, -7.11), p < 0.01] and reduced VAS [MD=-1.65 (95 % CI: -1.83,–1.48), p < 0.01] compared to NSAID therapies alone. Conclusion The existing weak evidence suggests that Baduanjin exercise may have favourable effects for KOA patients. However, further rigorously designed RCTs are warranted before it can be recommended