4 dioxanone (DON) and polyethyleneglycol (PEG) were carried out with stannous octoate (Sn(Oct)2) as a catalyst to prepare block copolymer (PDON-b-PEG-b-PDON).The results of 1H-NMR spectrochemical analysis showed the composition of block copolymers could be adjusted by varying the feeding ratio of PEG and DON.The Tm and crystallinity of PEG block in the block copolymers decreased greatly with the increase of PDON content.The water absorption percentage of block copolymer was also improved compared with that of PDON.