To study the effect of platelet lysate (PL) on chondrogenic differentiation of human umbilical cord derived mesenchymal stem cells (hUCMSCs) in vitro. Umbilical cords were voluntarily donated by healthy mothers. The hUCMSCs were isolated by collagenase digestion and cultured in vitro. The surface markers of the cells were detected by flow cytometer. According to different components of inductive medium, the cultured hUCMSCs were divided into 3 groups: group A H-DMEM medium, 10% fetal bovine serum (FBS), and 10%PL; group B H-DMEM medium, 10%FBS, 10 ng/mL transforming growth factor beta1 (TGF-beta1), 1 x 10(-7) mol/L dexamethasone, 50 microg/mL Vitamin C, and 1% insulin-transferrin-selenium (ITS); and group C (H-DMEM medium, 10%FBS, 10 ng/mL TGF-beta1, 1 x 10(-7) mol/L dexamethasone, 50 microg/mL vitamin C, 1%ITS, and 10%PL). The hUCMSCs were induced in the mediums for 2 weeks. Toluidine blue staining was used to detect the secretion of chondrocyte matrix. Immunofluorescence method was used to identify the