Objective: To evaluate the efficacy and side effects of mirtazapine and maprotiline in the treatment of treatment - resistant depression (TRsD). Methods: The patients were randomly assigned into mirtazapine group and maprotiline group (control group). The efficacy and side effects were assessed with Hamilton depression scale (HAMD), Hamilton anxiety scale (HAMA), clinical global impression (CGI - SI) and the treatment emergent scale (TESS) before and after 1,2,4,6 weeks treatment respectively. Results: In mirtazapine group, the HAMD and HAMA scores decreased from 31. 5 to 17.2 and from 24. 7 to 14.4. And they decreased from 32.2 to 22.7 and from 26.9 to 21.5 in maprotiline group. The cases improved were respectively 12 and 4 in the two groups. Mirtazapine was more effective and had fewer side effects than Maprotiline in the treatment. Conclusions: The curative effect of Mirtazapine is better than that of Maprotiline in the treatment of treatment - resistant depression.