[Objective] To study the efficacy and safety of total knee arthroplasty (TKA) and unicondylar arthroplasty (UKA) in the treatment of simple knee medial compartment osteoarthritis. [Methods] From July 2017 to June 2020, patients with simple knee medial compartment osteoarthritis treated by TKA and UKA were selected, and the operation indexes, postoperative functional rehabilitation indexes, knee joint function indexes, pain and osteoarthritis indexes and surgical complications of the two groups were studied and analyzed. [Results] Operation-related indexes and postoperative functional rehabilitation indexes (first straight leg elevation, active flexion and extension time, hospitalization time) of patients in UKA group were significantly lower than those in TKA group (P<0.05). After operation, knee joint function indexes, pain and osteoarthritis indexes of patients in both groups were significantly improved compared with those before operation (P<0.05). However, the pain, osteoarthritis and knee joint function of patients in UKA group were improved more obviously than those in TKA group (P<0.05). [Conclusion] Both surgical methods can effectively treat simple knee medial compartment osteoarthritis, but from the short-term curative effect, UKA has the advantages of less trauma, more obvious pain relief and better recovery of knee joint function.