Objective To explore the changes of helper T lymphocytes （Th）1 and Th2 subtypes in patients with depression and their relationships with the efficacy of antidepressant treatment. Methods A total of 37 patients with depression treated in Beijing Anding Hospital affiliated to Capital Medical University from October 2020 to December 2021 were selected as depression group. Another 39 healthy individuals whose age and gender matched were enrolled as the control group. The 17-item Hamilton Depression Rating Scale （HAMD-17） was used to evaluate the disease severity of the patients. The reduction rate of HAMD-17 score before and after treatment was calculated. It was treatment response if the score reduction rate is equal or higher than 50%， otherwise it was treatment non-response. The proportion of Th1 and Th2 cells in peripheral blood of all subjects was detected by flow cytometry， and the differences of Th1 and Th2 cell ratio between depression group and control group was compared before treatment. Patients with depression were treated with antidepressants for 8- 12 weeks. The proportion of Th cells in the treatment response group and the treatment non-response group were compared before and after treatment. Spearman correlation analysis was used to analyze the correlation between the proportion of Th cell subsets and HAMD-17 score. Results The proportion of Th1 cells in depression group was （43.61±24.27）% before treatment， which was higher than that in control group （26.13±18.56）%. The difference was statistically significant （t=-3.538， P＜ 0.01）. After antidepressant treatment， the total score of HAMD-17 in the depression group was （10.73±7.02）， lower than that before treatment （20.68±4.24）， and the difference was statistically significant （t=8.566， P＜ 0.01）. A total of 31 patients completed the detection of Th cells after treatment. The patients were divided into treatment non-response group （13 cases） and treatment response group （18 cases）. Repeated measurement analysis of variance showed that the interaction of group and time had a statistically significant effect on the proportion of Th1 cells （F=7.306， P=0.011）； The proportion of Th1 cells in the treatment non-response group before treatment was higher than that in the treatment response group ［（7.19±1.62） vs （5.31±2.38）］， and lower than that before treatment ［（4.29±2.10） vs （7.19±1.62）］， the difference was statistically significant （all P ＜ 0.01）. Correlation analysis showed that the score reduction rate of HAMD-17 in patients with depression before and after treatment was negatively correlated with the proportion of Th1 cells before treatment （r=-0.429， P=0.008）， negatively correlated with the ratio of Th2/Th1 cells before and after treatment （r=-0.357， P=0.048）， and positively correlated with the proportion of Th1 cells before and after treatment （r=0.591， P＜ 0.001）. Conclusions The detection of Th1 cell proportion in peripheral blood is helpful for early prediction of the antidepressant efficacy in patients with depression.