Chitosan was added to kamaboko gels made from grass carp (Ctenopharyngodon idellus), and the effects on preservation quality were determined by biochemical (pH, total volatile basic nitrogen [TVBN], thiobarbituric acid [TBA], peroxide value) and microbiological (total bacterial count) determinations during storage at 4C. Application of chitosan, at a level of 1% (w/w), exhibited a beneficial effect on inhibiting lipid oxidation and bacterial growth in the gels. The preservative function was related to the molecular weight of chitosans. Relative low molecular weight chitosan showed a higher antioxidant capacity than high molecular weight chitosan. However, mixture of 300 and 10 kDa chitosans exhibited the highest antibacterial activity. Increases of pH, TVBN, TBA and peroxide values in gels during storage were significantly reduced when chitosan was applied. The present study provides a possible application of chitosan as a food additive for surimi-based foods.