Scientific value: - The thesis provided evidence on the efficacy and safety of narrow-band UVB treatment for psoriasis vulgaris based on Minimum Erythema Dose (MED): 76.79% of patients achieved PASI 75 after 36 exposures and the average dose was 226.79 ± 44.32 mJ / cm2; the average number of exposures to achieve PASI 75 was 25.20 ± 7.30 times; the mean total cumulative dose of the group achieving PASI 75 was 18778.9 ± 8217.6 mJ / cm2; patients quality of life was significantly improved; the most common side effect was hyperpigmentation (97.67%).