Abstract: This study focuses on crayfish shrimp paste as the research subject, with the addition of 0, 20%, and 40% shrimp shell powder, respectively. Across three fermentation stages of 0, 6, and 12 days for the crayfish shrimp paste, an investigation into the flavor and microbial evolution was conducted utilizing electronic noses, gas chromatography-mass spectrometry (GC-MS), and 16S rRNA sequencing. The results showed that adding shrimp shell powder could significantly increase the types and contents of volatile flavor compounds (sulfur compounds, amines, ketones, esters and heterocycles) in shrimp paste samples, and adding 20% shrimp shell powder could better promote the production and growth of volatile flavor compounds. Combining Odor activity value (OAV) and Variable Importance for the Projection, VIP) screened out three substances (2-decanone, methylmercaptan, dimethyl trisulfide) as the signature flavor compounds to distinguish the difference of different addition amounts of shrimp shell powder and different fermentation time. The addition of shrimp shell powder increased the abundance and diversity of microbial genera (Oceanobacillus, Virgibacillus, Cerasibacillus). Combined with Spearman correlation coefficient analysis, it was found that the unique Virgibacillus in the shrimp shell powder sample group showed significant positive correlation with several key flavor compounds and contributed the most to flavor. In summary, adding shrimp shell powder to lobster paste, especially when the amount is 20%, is conducive to promoting the growth of flavor-related microorganisms and enriching the flavor of shrimp paste.