Abstract: Coated and uncoated poly (glycolic acid) (PGA) sutures were investigated in phosphate buffer solution (PBS) (pH=7.4) at 37 ℃ for six weeks. The in vitro degradation behavior was studied by methods of DSC、XRD and SEM, exploring the impact of coating on PGA suture degradation performance. The results show that coating can extend the degradation time of PGA sutures. The mass loss of coated PGA sutures is slower than uncoated sutures and the breaking strength retention rate is greater than uncoated sutures. Degree of crystallinity of PGA sutures in the degradation gradually increased first and then gradually decreased which is related to the degradation of poly (lactide-co-glycolide) (PGLA). The melting point of crystalline region of PGA sutures is substantially decreased, but the scope of change in the melting temperature of coated suture is less than that of uncoated suture. The results of SEM show that there are transverse ruptures on the uncoated PGA suture after 35 d of degradation and the skeleton of inside suture remains intact after 42 d of degradation.