Psoriasis is a common chronic relapsing autoimmune skin disease in dermatology. For patients with mild plaque psoriasis, drug therapy often achieves satisfactory results. However, moderate to severe psoriasis often involves the entire body, and drug therapy has limited efficacy and is prone to relapse. Therefore, in recent years, there has been a growing interest in narrowband ultraviolet B (NB-UVB) phototherapy for moderate to severe psoriasis. NB-UVB irradiation is considered a safe and reliable treatment for psoriasis.