Objective To systematically review the efficacy of low-frequency repetitive transcranial magnetic stimulation (rTMS) compared with sham therapy for the treatment of major depressive disorder. Methods The Cochrane Library, Medline, EMbase, CBMdisk, CNKI and VIP were searched through computer from 1985 to 2011. The review included RCTs comparing the treatment efficacy of low-frequency rTMS located on right dorsolateral prefrontal cortex (DLPFC) with sham stimulation in the patients suffering major depressive disorder. The quality of the included RCTs was strictly evaluated and the data were extracted by two reviewers independently. The extracted data were analyzed by RevMan 4.2. Results Among seven double-blinded RCTs involving 234 patients included, 1 was A level in quality, 5 were B level, and 1 was C level according to the outcomes of quality evaluation. The results of Meta-analysis indicated that low frequency rTMS was superior to sham stimulation in remission rates after two weeks’ treatment (RR=3.11, 95%CI 1.56 to 6.19). Additionally, low frequency rTMS was lower than the sham stimulation in the scores of HDRS and MADRS (WMD= –6.41, 95%CI –9.32 to –3.50, and WMD= –5.27, 95%CI –9.08 to –1.46, respectively). But no significant difference in response rates between the low prequency rTMS group and the sham group was found (RR=1.72, 95%CI 0.74 to 4.01). There were no severe and intolerable side effects reported in these seven studies. Conclusion The low frequency rTMS as a non-invasive and safe technique may appear to be effective for the treatment of major depressive disorder according to the positive results but the conclusion is not definite because of negative results. This review suggests that parameters could be sited as frequency: 1 Hz, intensity: 90%-110% motor threshold (MT), location: right DLPFC and duration: 2 weeks. Nevertheless, further multicenter and high quality studies are needed before it is used as a first-line treatment for major depressive disorder.