The changes in basic physicochemical properties and microbial diversity of Douchi before and after efflorescence of the surface were evaluated. The physicochemical properties were investigated via determining the content of moisture, ash, crude protein, crude fat, total sugar, reducing sugar, total acid, and amino nitrogen, along with the amino acid composition. The microbial diversity was measured by Illumina Miseq sequencing. The results showed that, with the progress of efflorescing, the ash and total sugar content of Douchi exhibited insignificant changes, and the crude fat, reducing sugar and total acid content showed a downward trend as a whole. The moisture content increased first and then kept stable. An adverse trend was observed on amino nitrogen content as compared to that of the crude protein content between 0~6 days. The amino acid score illustrated that the nutritional value of protein decreases after efflorescing. According to the results of Illumina Miseq sequencing, the bacteria and fungi OTUs of Douchi were all reduced after efflorescing, and the ratio of Bacillus in bacteria was increased, with the ratio of Aspergillus in fungi reduced. Therefore, the efflorescing would reduce the nutritional value of Douchi and decrease the diversity of bacterial community. However, the diversity of fungal community could be increased, with the destroy of the original flora composition.