Abstract: Increasing evidence support multiple biological activitied factors and plasma proteins released in the activated platelet rich plasma (PRP) play crucial roles in the mechanism of cartilage repair such as promoting proliferation of chondrocytes, stimulating vertical migration, proliferation, chondrocytes differentiation and the synthesis and secretion of cartilaginous matrix in bone mesenchymal stem cells (BMSCs) and immature chondrocytes. In addition, PRP can protect the chondrocytes via anti-inflammation, stimulating synoviocytes to secrete hyaluronic acid (HA) as well as synovial fluid, and forming gel as initial tissue for wound healing and three-dimensional substrate for progenitors proliferation and differentiation. Understanding mechanisms of PRP in cartilage repair will benefit for improving its therapeutic efficacy.