In order to make clear the effect of synovial fluid on the wear behavior of high molecular weight polyethylene(UHMWPE), which is the commonly used material of artificial acetabular cup, a series of wear tests were carried out by sliding HUMWPR against pig hip joint in boundary lubrication of various concentration of hyaluronic acid and proteins. It is found that the wear of UHMWPE is strongly influenced by the content of hyaluronic acid and the protein components such as albumin and γ-globulin. When the synovial fluids were only composed by isotonic sodium chloride solution containing 0.1wt% hyaluronic acid, the minimum weight loss of UHMWPE was observed. It was evidenced that there exists a certain kinds of proteins and corresponding components that can mostly decrease the wear of UHMWPE.