Abstract: We added different doses of carboxymethyl agar (CMA) to tilapia (Oreochromis niloticus×O. areus) surimi to investigate the effects of CMA on the gel properties of tilapia surimi based on the indexes such as surimi gel strength, water holding capacity, texture characteristics, color, protein chemical composition and microstructure. The results show that CMA could significantly increase the gel strength of surimi gel with the addition of 0.5%−2.0% CMA (P<0.05), reaching the maximum value of 70.7%. The water holding capacity, texture characteristics and whiteness could be improved significantly by adding 1.5%−2.5%, 1.5%−2.5% and 0.5% CMA, respectively (P<0.05). CMA had a significant effect on the chemical force of surimi protein (P<0.05), showing that moderate addition of CMA destroyed the ionic bond, promoted the formation of hydrogen bond, hydrophobic bond and disulfide bond, and promoted the gelation of surimi. SDS-PAGE electrophoresis and scanning electron microscopy analysis show that CMA promoted the cross-linking of myosin heavy chains (MHC), and the addition of 1.5% CMA could make the surimi gel form a uniform and dense network structure. In conclusion, moderate addition of CMA to tilapia surimi affected the water absorption, chemical force and protein thermal aggregation behavior of the surimi, enhanced the crosslinking effect of protein, improved the network structure of surimi gel, and reformed the gel properties of surimi.