Objective To explore the correlation of serum IL-17 and IL-26 levels with skin lesion severity (evaluated by PASI), as well as the expression of Th17 and Th22 cells in patients with psoriasis vulgaris. Methods A total of 43 healthy subjects who underwent physical examination in Luotian County Psychiatric Hospital from March 2023 to January 2024 were selected as the control group. Meanwhile, 43 patients with psoriasis vulgaris (30 patients in progressive stage and 13 patients in stable stage) were selected as the observation group. The immune regulation indexes were compared between the two groups, and the immune regulation indexes and PASI were compared among different stages. The correlations of IL-17 and IL-26 with disease stage, Th17, Th22 and PASI were analyzed. Results The levels of IL-17, IL-26, Th17 and Th22 in the observation group were higher than those in the control group (P <0.05). The levels of IL-17, IL-26, Th17 and Th22 in the progressive stage were higher than those in the stable stage (P <0.05). There was no statistically significant difference in PASI among different stages (P >0.05). IL-17 and IL-26 were positively correlated with disease stage, Th17, Th22 and PASI (P <0.001). Conclusion There are differences in the expression of immune regulation indexes between patients with psoriasis vulgaris and healthy people. The expression of these indexes increases in the progressive stage. The levels of IL-17 and IL-26 are positively correlated with disease stage, Th17/Th22 cell ratio and PASI score.