Corticosterone (CORT) is one of the most important glucocorticosteroid in birds. When subjected to human interference, capture, harsh environment and other stress stimulation, the hypothalamic-pituitary- adrenal (HPA) axis is activated and corticosterone would be synthesized in large quantities, which then modifies physiology and behavior. Capture followed by the collection of blood samples over 5﹣30 min is a widely used stressor in studies of stress-induced corticosterone in birds. Stress-induced corticosterone is essential for individual survival. However, current results on the changes of plasma stress-induced corticosterone during the breeding seasons and its relationship with reproduction are significantly different, and experimental studies in different species are still needed. In our study, Varied Tits (Sittiparus varius) were caught with mist nets in the courtship periods (from March to April in 2019); and about 50 μl blood samples were taken by puncturing the brachial vein within 10﹣15 min. Parental birds were captured with nest-box traps when the nestlings were 6﹣8 days old, and blood samples were taken within 10﹣15 min. After centrifugalization, all blood plasma samples were analyzed for stress-induced corticosterone concentration by avian corticosterone ELISA kit. Independent sample t-test was used to compare the stress-induced corticosterone concentration during the courtship periods and nestling feeding periods. Multiple linear regression analysis was used to analyze the relationships between stress-induced corticosterone of parental birds in nestling feeding periods and the reproductive investment of Varied Tits. The results showed that, compared with the courtship periods, the stress-induced corticosterone concentration of Varied Tits increased significantly in nestling feeding periods (female: t(29, 29) =﹣10.782, df = 56, P < 0.05; male: t(50, 31) =﹣10.207, df = 43.099, P < 0.05; Fig. 1). And there was no significant difference between male and female parental birds (courtship: t(29, 50) =﹣0.684, df = 77, P > 0.05; nestling breeding period: t(29, 31) = 0.078, df = 58, P > 0.05; Fig. 1). The concentration of stress-induced corticosterone had no significant effect on reproductive parameters (P > 0.05; Fig. 2), feeding investment and nest defense (P > 0.05; Fig. 3). Our studies presented differences of plasma stress-induced corticosterone in breeding seasons of Varied Tits, and provided scientific basis for the researches and protection of Varied Tits.