Objective To observe the efficacy of adalimumab for treatment of patients with moderate to severe plaque psoriasis and the changes of serum 25(OH)D level. Methods A total of 42 patients, who were clinically diagnosed with moderate to severe psoriasis and were not improved by normal psoriatic treatment, were given adalimumab subcutaneously(80 mg at week 0, and then 40 mg every other week for totally 12 weeks). The changes of serum 25(OH)D level, psoriasis area and severity index (PASI), the doctor comprehensive assessment indicators (PGA) and dermatology life quality index (DLQI) scores were observed and analyzed. Results Totally 41 patients completed the treatment. At week 12, 32 patients (78.0%) achieved PASI75 (greater than or equal to 75% improvement in PASI score) response, while 9 patients (22.0%) did not. The scores of PASI, PGA and DLQI were all significantly lower after treatment compared with those before treatment (P<0.01). The serum 25(OH)D level after treatment was significantly higher than that before treatment (P<0.01). No severe adverse events were observed during the experiment. Conclusion Adalimumab is effective for treatment of moderate to severe plaque psoriasis, and the serum 25(OH)D level is increased after treatment, which might be related to mechanism of the effect of adalimumab.