Objective To systematically review the related research on the effects of light therapy on sleep， cognition and behavior of patients with Alzheimer disease， aiming to provide reference for improving the symptoms of Alzheimer disease. Methods Through the database retrieval of literature， based on the inclusion and screening criteria， extraction of data and literature quality evaluation， meta-analysis was conducted. Results Finally， 15 studies were included， all of which were randomized controlled designs， and the quality of the literature was relatively good. The analysis results showed that light therapy can improve the quality of sleep （SMD=0.56， 95%CI：0.38-0.75， P＜ 0.01）， cognition （SMD=0.39， 95%CI： 0.10-0.67， P＜ 0.01） and behavior obstacles （SMD=0.82， 95%CI：0.61-1.02， P ＜ 0.01）. Conclusions Light therapy can effectively improve sleep quality， cognitive level and behavior disorders in patients with Alzheimer disease.