Abstract: Taking the ultra-fine fish bone paste prepared from cod bones as the object, the conditions of enzymatic hydrolysis of fish bone paste were optimized by using the single factor experiment and response surface design based on the degree of hydrolysis as an indicator. Meanwhile, the changes of flavor characteristics of fish bone paste and its hydrolysates were analyzed by employing electronic nose, electronic tongue, gas-phase ion migration chromatography(GC-IMS), and free amino acid determination. The results showed that the optimal enzymatic hydrolysis conditions were obtained at hydrolysis time of 5 hours, enzyme addition of 1.0%, material-liquid ratio of 1:1 by using flavor protease, yield 43.8% of hydrolysis degree. The electronic nose analysis results showed that the aromatic substances in the hydrolysate increased, while the content of undesirable compounds such as alkanes and ammonia decreased. The results of electronic tongue analysis showed that the acidity of the hydrolysate was increased, while the bitterness was reduced, and the overall taste was good and rich. There were 29 volatile compounds of hydrolysate and fish bone paste were detected by GC-IMS. In fish bone paste, the main volatile flavor substances were aldehydes and ketones, and the main flavor substances in the hydrolysate were ketones and esters. These types and contents of volatile flavor substances were significantly different. The hydrolysate increased the content of flavored amino acids and the hydrolysate had a good flavor.