Objectives: This study aims to assess the efficacy of UVBnb phototherapy alone, and with methotrexate in plaque psoriasis, and comparing the side effects and relapse between the two kinds of treatments. Study Design: randomized experimental study. Methods: A total of 40 psoriasis patients were included in the study, 16 patients were treated with UVBnb and methotrexate, whereas 24 patients were treated with UVBnb alone. PASI was calculated for every patient every 2 weeks through treatment, and every 4 weeks after clearance. Side effects and relapse were compared between two kinds of therapy. Results: there were no statistical important differences between two groups of study according to clearance, clearance rate in combination group was 75% vs. 46% in phototherapy group, tanning and hyperpigmentation were the most common side effects for both groups, recurrence rate was 22.7% in study patients, all of them were from phototherapy group. Conclusion: this study revealed that UVBnb phototherapy alone,and with methotrexate have the same efficacy in the treatment of psoriasis, and the combined therapy with methotrexate reduce the number of UVBnb treatments necessary for clearance. Side effects were tolerated in both kinds of treatments. Relapse after clearance occurs more likely with alone UVBnb phototherapy.