Objective：To observe the level of serum leptin in psoriasis and psoriasis with metabolic syndrome（MS） before and after the treatment and to analyze its clinical significance. Methods：Data of height，weight，waistline，psoriasis area and severity index，fasting plasma glucose，blood pressure，blood lipid and MS of psoriasis patients were collected. Patients were divided into two groups according to whether they were suffering from MS. Serum leptin of patients was tested and compared with that of normal group. Results：Duration of psoriasis with MS was longer than that without MS，and patients with MS had poor treatment effect. Before treatment，serum leptin level was higher in all psoriasis patients than in normal controls（P=0.000） and leptin level was the highest in psoriasis with MS. After treatment，leptin level was decreased slightly in psoriasis with MS（P=0.209），but was significantly decreased in psoriasis without MS（P=0.000）. Conclusions：Traditional treatment is ineffective for psoriasis with MS and leptin may involve in the resistance.