Objective To explore the efficacy of bright light therapy （BLT） as an adjunctive therapy for non-seasonal depressive disorder on the basis on drug treatment. Methods A total of 33 patients with non-seasonal depression hospitalized in the Mental Health Center of the First Hospital of Hebei Medical University from September 2020 to January 2021 were selected as the research subjects. According to the random number table method， they were divided into BLT group （17 patients） and dim light therapy group （16 patients）. Based on drug treatment， BLT adjuvant treatment and dim light treatment were given in the morning for 2 weeks. The scores of 17-item Hamilton Depression Scale （HAMD-17） and Clinical Global Impression （CGI） were compared between the two groups before treatment and at the end of the second week of the treatment； The scores of 16-Item Quick Inventory of Depressive Symptomatology Self-Report （QIDS-SR16） were compared between the two groups before treatment and at the end of the first week of treatment. The clinical response rate of the two groups at the end of the second week of treatment was compared， and the onset time of treatment was evaluated. Results 15 participants in the BLT group and 12 participants in the dim light therapy group completed this study. There were 7 patients with moderate depression and 8 patients with major depression in the BLT group， 7 patients with moderate depression and 5 patients with major depression in the dim light therapy group. Before the treatment， the score of cognitive impairment factor in BLT group was higher than that in dim light therapy group ［2.00（1.67，2.00） vs 1.33（0.75，1.90）］， and the difference is statistically significant （Z= -2.777，P＜ 0.01）. At the end of the second week of treatment， the total HAMD-17 score， anxiety somatization factor score， and disease severity score were statistically significantly lower in the BLT group than those in the dim light therapy group ［（9.40±4.15） vs （13.75±5.61）， （0.56±0.38） vs （1.00±0.53） and 2.00（1.00，3.00） vs 3.00（3.00，4.00）； P ＜ 0.05］. The change of cognitive impairment factor scores before and after treatment in the BLT group was higher than that in the dim light therapy group ［1.31（1.00，1.34） vs 0.33（0，1.17）］. The difference was statistically significant （Z=-2.680， P＜ 0.01）. The clinical response rate of BLT group was 8/15， which compared with 4/12 of the dim light therapy group， showing no statistically significant difference （P ＞ 0.05）. The onset time of treatment was 5.14 days in the BLT group. No effect was found within 1 week in the dim light therapy group. Conclusions BLT， as an adjunctive therapy， can improve depressive symptoms and reduce disease severity quickly and effectively for patients with non-seasonal depressive disorder.