Psoriasis is an inflammatory skin disease. The correlation between intestinal microbiota and immune-mediated diseases makes scientists pay attention to the pathogenic role of microbiota. The aim of this study was to identify the gut microbial composition of patients with psoriasis. 16S rRNA gene sequencing method was used to analyse the faecal samples which was collected from 28 moderately severe psoriasis patients and 21 healthy controls and was followed by the analysing of informatics methods. No visible differences can be observed in the diversity of gut microbiota between the psoriasis and the healthy patients, but the composition of the gut microbiota illustrate significant distinction between these two groups. At the phylum level, compared to the healthy control group, the psoriasis group shows higher relative abundance of Bacteroidetes and lower relative abundance of Proteobacteria (P < 0.05). At the genus level, unidentified_Enterobacteriaceae, unidentified_Lachnospiraceae, Romboutsia, Subdoligranulum, unidentified_Erysipelotrichaceae, Dorea were relatively less abundant in psoriasis patients, whereas Lactobacillus, Dialister were relatively more abundant in psoriasis group (all P < 0.05). LefSe analysis (linear discriminant analysis effect size) indicated that Negativicutes and Bacteroidia were potential biomarkers for psoriasis. This study identified the intestinal microecological environment of patients with psoriasis and healthy people, proving that psoriasis patients have a remarkably disturbed microbiome, and found several biomarkers of intestinal microorganisms in patients with psoriasis.