Objective To investigate the efficiency and safety of infra-low-frequency transcranial magnetic stimulation (TMS) in the treatment of depressive symptoms in Alzheimer’s disease (AD) patients. Methods A randomized, controlled and single-blinded trial was conducted on 47 AD patients with depressive symptoms admitted in our hospital from August 2014 to August 2015. The patients were randomly divided into the treatment group (n＝23) and the control group (n＝24). The patients of the former group was treated by mirtazapine combined with infra-low-frequency TMS for 4 weeks, while those of the latter group received sham infra-low-frequency TMS and mirtazapine treatment. The geriatric depression scale (GDS) was used to assess the depressive symptoms before, and after 2 and 4 weeks treatment to evaluate the curative effect by the total efficacy. Results After 2 weeks’ treatment, GDS score was significantly lower in the treatment group than in the control group [(13.43±2.57) vs (16.08±3.96), P＜0.05], but there was no significant difference in the score between the 2 groups [(9.48±3.11) vs (9.67±3.95), P＞0.05] in 4 weeks. There existed significant difference in the total efficacy between the 2 groups after 2 weeks’ treatment (Chi square＝4.776, P＝0.029), but no difference after 4 weeks (Chi square＝3.297, P＝0.348). Conclusion Infra-low-frequency TMS combined with mirtazapine has a shorter onset time and better short-term efficacy than medication alone in the treatment of depressive symptoms in AD patients.