Abstract: The poor gel properties of fish gelatin (FG) limit its application in production. Chitosan (CS) and glutamine transaminase (TG) have been proved to be able to improve the gel properties of FG. In this study, TG and CS were used to modify FG, producing two kinds of modified gelatin: FG-TG and FG-TG-CS. The effects of two modification methods on the strength, texture characteristics, rheological properties, fluorescence intensity, infrared spectrum and in vitro digestibility of FG gel were compared. The findings revealed that both single and complex modifications could greatly improve the gel strength and textural qualities of FG. As CS addiction was 0.7%, the complex modified FG had the highest gel strength and hardness, which were 522.02±0.07 g and 11.79±0.30 N, respectively. Rheological results revealed that the complex modified gelatin had the maximum viscosity (η₅₀=0.53±0.04 mPa·s), gelling points (23.04±0.17 ℃), and melting points (31.30±0.25 ℃). Modification decreased the fluorescence intensity of the samples and complex modification showed higher fluorescence quenching effectiveness. Fourier transform infrared spectroscopy redshift indicated that the complex modification boosted the α-helix content in the system, stabilize the formation of colloids. Thus, the TG-CS complex modification effectively solve the shortcomings of weak gelling properties.