Objective To explore the mechanism of adaptive cognitive emotion regulation strategies and psychological flexibility in the relationship between perceived stress and depressive emotion in patients with depressive disorder. Methods Convenience sampling was used to select 204 patients with depressive disorder who attended the Third Hospital of Daqing City of Heilongjiang Province from December 2021 to December 2022 as study subjects. The Chinese Perceived Stress Scale （CPSS）， Comprehensive assessment of Acceptance and Commitment Therapy （CompACT）， Cognitive Emotion Regulation Questionnaire （CERQ）， and Self-Rating Depression Scale （SDS） were used to assess the patients' perceived stress， psychological flexibility， adaptive cognitive emotion regulation strategies， and depressive emotion. Pearson correlation was used to analyze the correlations between perceived stress， psychological flexibility， adaptive cognitive emotion regulation strategies， and depressive emotion. The common method bias testing was performed using the Harman one-way method， the mediating effect analysis was performed using Model 6 in the Process program， and the significance of the mediating effect was tested using the bias-corrected bootstrap method. A total of 215 questionnaires were distributed in this study， and 204 valid questionnaires were recovered, with an effective recovery rate of 94.88%（204/215）. Results Perceived stress in 204 depressive disorder patients negatively predicted adaptive cognitive emotion regulation strategies （β= -0.51， P＜ 0.01） and psychological flexibility （β=-0.43， P＜ 0.01） and positively predicted depressive emotion （β=0.36， P＜0.01）. Adaptive emotion regulation strategies positively predicted psychological flexibility （β=0.40， P ＜ 0.01）. Psychological flexibility negatively predicted depressive emotion （β=-0.35， P ＜ 0.01）. The above differences were statistically significant. Psychological flexibility mediated the association between perceived stress and depressive emotion ［95%CI （0.09，0.25）］， with the mediating effect accounting for 24.64% of the total effect. Psychological flexibility and adaptive cognitive emotion regulation strategies had a chain mediating effect between perceived stress and depressive emotion ［95%CI （0.03， 0.15）］， with the mediating effect accounting for 11.59% of the total effect. Conclusions Perceived stress in patients with depressive disorder not only act directly on the depressive emotion， but also indirectly through the chain mediation of adaptive cognitive emotion regulation strategies and psychological flexibility.