Objective To compare the effects of Acceptance Commitment Therapy(ACT) and Cognitive Behavior Therapy(CBT) on anxiety and depression in the elderly,and to explore the psychological mechanism of ACT to improve anxiety and depression.Methods A total of 25 elderly people were screened from four communities in Beijing.According to the place of residence,12 persons were enrolled in the ACT group and 13 persons were enrolled in the CBT group.The mindful attention awareness scale,geriatric anxiety inventory,geriatric depression scale,the acceptance and action questionnaire-Ⅱ and cognitive fusion questionnaire were evaluated before regrouping (T1),after six regiments (T2) and 5 weeks after the end of the intervention (T3).Results (1) On the level of mindfulness,the score of ACT group was higher than that in CBT group at T2(ACT:80.31 ±6.18,CBT:74.20±4.48,t=2.52,P＜0.05) and T3 (ACT:82.20±4.48,CBT:70.00± 12.23,t=4.56,P＜0.01).(2) On the level of anxiety there was significant difference between the two groups at T2(ACT:2.88±1.86,CBT:8.87±2.80,t=-8.15,P＜0.01) and T3(ACT:5.38±2.02,CBT:10.50±2.66,t=-6.93,P＜0.01),and ACT group was higher than the CBT group.(3)On the levels of depression there was significant difference between the two groups at T 1 (ACT:4.59 ± 3.97,CBT:7.89± 6.39,t =-2.25,P＜0.05),the ACT group was lower than the CBT group.The CBT group on the levels of depression there was a significant difference T1 and T2 (t=2.92,P＜0.05).(4) On the level of psychological flexibility,there was a significant difference between the two groups at T2 (ACT:41.38 ± 8.28,CBT:49.60± 3.52,t =-3.64,P＜0.01)and T3(ACT:40.80±7.66,CBT:52.47±6.23,t=-4.98,P＜0.01),and ACT group was lower than the CBT group.(5) Empirical avoidance only achieved a significant level of intermediate effects between ACT therapy and anxiety.In the ACT group,the median effect of empirical avoidance on anxiety was 11.40％.Conclusion The effect of CBT on depression is better than that of ACT,while the effect of ACT on the level of mindfulness,anxiety and mental flexibility is better than that of CBT.ACT with psychological flexibility as a psychological mechanism can improve the mental flexibility of the individual more than the CBT.