Two groups of subjects will be included 55 subjects in electroacupuncture with 2Hz group, 55 subjects in the electroacupuncture with 100Hz group. The clinical efficacy of electroacupuncture with different frequencies (2 Hz, 100 Hz) in the treatment of MDD will be observed by evaluation indicators, such as Self-rating depression scale and Hamilton depression scale.

Inclusion Criteria:

1. Patients suffering from MDD in accordance with the diagnostic criteria;
2. Hamilton Depression Scale score is between 21 and 35 (mild to moderate MDD);
3. 18≤age≤60 years, both gender;
4. Patients who have not used antidepressants and other psychiatric drugs (including traditional Chinese medicine), or have used them but have stopped for at least 2 weeks;
5. Patients have clear consciousness and could communicate with others normally;
6. Patients could understand the full study protocol and written informed consent is provided by themselves. Note: Subjects who meet the above six items will be included.

Exclusion Criteria:

1. Patients with bipolar disorder;
2. Patients with schizophrenia or other mental disorders;
3. Patients with severe medical diseases, tumors or diseases of the central nervous system;
4. Patients suffering from severe depressive episode with psychotic symptoms;
5. Suicidal patients;
6. Patients with seasonal depression;
7. Patients with organic depression;
8. Patients with alcohol or drug addicts;
9. Patients using other therapies;
10. Patients in pregnancy or lactation;
11. Patients suffering from cognitive dysfunction, aphasia or other diseases that cannot cooperate with treatment;
12. Patients with pacemakers;
13. Patients who are not suitable for electroacupuncture.