Based on the equivalent sterilization intensity theory (F₀=12), this study systematically compared the effects of three high-temperature and high-pressure (HTHP) sterilization treatments (115 ℃/42 min, 118 ℃/30 min, 121 ℃/11 min) and 9 kGy irradiation sterilization on the quality of fish-lamb composite products. A comprehensive analysis of key flavor compounds was conducted by measuring crude protein, crude fat, thiobarbituric acid reactive substances (TBARS), free amino acids, flavor nucleotides, electronic tongue response, gas chromatography-ion mobility spectrometry (GC-IMS), and sensory characteristics. The results indicated that compared to HTHP treatments, irradiation had a lesser impact on crude protein and crude fat content, and exhibited the smallest reduction in equivalent umami concentration (EUC) (33.99%), suggesting better umami retention. However, GC-IMS analysis revealed that irradiation induced the formation of typical off-flavor compounds, such as butanal and 2-methylbutanal, which led to a significantly lower sensory score (P<0.05) of only 71. HTHP sterilization significantly promoted protein hydrolysis, resulting in a significantly higher total free amino acid content compared to the irradiation group (P<0.05). Under the equivalent F₀ value, different temperature-time combinations of HTHP treatments significantly affected the flavor profile. The 115 ℃/42 min (low-temperature long-time) treatment caused the most severe flavor deterioration, characterized by a 24.30% loss in total free amino acids, a 35.61% decrease in umami amino acids, and a significant 65.79% reduction in inosine monophosphate (IMP) content. In contrast, the 118 ℃/30 min treatment group demonstrated the highest EUC value (10.74 mg MSG/g) and sensory acceptability. In conclusion, under the prerequisite of ensuring equivalent sterilization intensity, the 118 ℃/30 min HTHP process is identified as the optimal sterilization method for the fish-lamb product, effectively ensuring microbial safety while preserving its flavor quality. This study provides an important theoretical basis for the optimization of sterilization processes for similar fish-lamb composite products.