Abstract: Huang Yingmei, Bi Jianping, Zhang Hongying, Li Jun, Qu Caijie, Wang Qingyi, Huang Yong, Jiang Yuxia Department of Dermatology, Qingdao Municipal Hospital, Qingdao University, Qingdao 266011, China Corresponding author: Zhang Hongying, Email: zhhy1023@163.com 【Abstract】 Objective To investigate the effects of narrow-band ultraviolet B （NB-UVB） therapy on the levels of plasmin and CC chemokine ligand 20 （CCL20） in peripheral blood of patients with psoriasis vulgaris. Methods A total of 60 patients with psoriasis vulgaris in progressive stage were treated with NB-UVB radiation thrice a week for 8 weeks. Enzyme-linked immunosorbent assay （ELISA） was performed to detect the levels of plasmin and CCL20 in the peripheral blood of the patients before and after the treatment, as well as in the peripheral blood of 50 healthy controls. Results After the treatment, psoriasis area and severity index （PASI） scores in patients were significantly decreased compared with those before the treatment （2.54 ± 1.64 vs. 10.26 ± 3.14, t = 17.40, P < 0.05）, and the response rate was up to 87% （52/60）. Before the treatment, levels of plasmin and CCL20 were both significantly higher in the patient group than in the control group （plasmin: 180.07 ± 40.62 μg/L vs. 76.30 ± 26.92 μg/L, t = 15.45, P < 0.05; CCL20: 422.41 ± 129.87 pg/L vs. 205.33 ± 49.89 pg/L, t = 11.15, P < 0.05）. After the treatment, levels of plasmin （148.22 ± 40.05 μg/L） and CCL20 （329.67 ± 100.73 pg/L） in patients were significantly decreased compared with those before the treatment （t = 4.97, 6.44, P < 0.05）, but still significantly higher than those in controls （t = 10.82, 7.95, P < 0.05）. Before the treatment, the level of plasmin was positively correlated with the level of CCL20 in peripheral blood of the patients （r = 0.57, P < 0.05）, and the levels of plasmin and CCL20 were both positively correlated with the PASI score （r = 0.49, 0.62, respectively, both P < 0.05）. Conclusion NB-UVB radiation may exert a therapeutic effect on psoriasis vulgaris by reducing levels of plasmin and CCL20 in peripheral blood of patients.