Oxidized sodium alginate (OSA) was prepared through an oxidation reaction of sodium alginate in the presence of sodium periodate. In situ crosslinked hydrogels were obtained through the crosslinking reaction between the active aldehyde of OSA and the amino of the carboxymethyl chitosan (CMCS). The effects of the addition of OSA on the structure and properties of the hydrogels are discussed. The structures of OSA, CMCS, and the hydrogels were analyzed by Fourier transform infrared spectroscopy, and the morphology of the hydrogels was characterized by X-ray diffraction and scanning electron microscopy. The results from the gelation time test show that the hydrogels had the shortest gelation time of 6.3 s when the addition of OSA was 8 mL. The results from the swelling degree determination test showed that the hydrogel swelling degree first increased and then decreased with the addition of OSA. With the introduction of nanosilver, the hydrogels showed a degree of antibacterial performance. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.