O-Carboxymethylchitosan (O-CMC) in 1000 g batch was prepared from chitin as starting material and its chemical structure was confirmed by analysis of IR and NMR. O-CMC solution, sodium hyaluronate (HA) solution and physiological saline were used in Sprague-Dawley rat model for prevention of postsurgical adhesions; after 7 days of an abdominal operation, the 3 groups were evaluated according to Belluco standard, the mean scores of O-CMC group, HA group and physiological saline group were 2.5 +/- 3.1, 3.3 +/- 3.6 and 10.3 +/- 1.0, respectively. Histological inspection showed that in O-CMC group, mesothelial cells on peritonaeum or cecum surfaces were almost restored; in HA group the injured surface of peritonaeum was mostly repaired, but in physiological saline group the injured surface of cecum was just a little repaired; there were extensive adhesions between peritonaeum and cecum, and inflammatory response was quite serious. Experimental results indicated that O-CMC and HA had excellent efficiency and O-CMC was slightly better than HA for the prevention of postsurgical adhesions.