[Objective] We studied the diversity and traced the source of microbial community in Pixian broad bean paste and its two semi-fermented products, including broad bean meju and chili moromi. In addition, we also characterized the flavor compounds in Pixian broad bean paste. [Methods] High throughput sequencing was used to explore the microbial community structure and succession. Meanwhile, high throughput liquid chromatography and gas chromatography-mass spectrometry were used to determine the concentrations of nonvolatile and volatile flavor compounds. Multiple bioinformatic methods were used to trace the microbes and flavor compounds in Pixian broad bean paste. [Results] Chili moromi contributes 44% to 59% bacterial communities and 42% to 77% fungal communities to Pixian broad bean paste fermentation. Broad bean meju contributes 5% to 22% bacterial communities and 2% to 18% fungal communities to Pixian broad bean paste fermentation. In addition, 16 bacterial genera were only contributed by chili moromi. Two bacterial genus and two fungal genera are only contributed by broad bean meju. In addition, 1-octen-3-ol, phenylacetaldehyde, isobutyraldehyde, malic acid and furfural were only traced from broad bean meju. Capsaicin, 3-methyl-1-butanol, hexanol and isobutanol were only traced from chili moromi. [Conclusion] Chili moromi contributes the main microbial communities to Pixian broad bean paste, while broad bean meju contributes the main substrates (including amino acids and glucose). Two semi-fermented products, including chili moromi and broad bean meju, contributed their unique microbes and flavor compounds to Pixian broad bean paste, which might be the reason why Pixian broad bean paste has the characteristic aroma and taste.