We developed the study on behavioral time budget daily rhythm of Mergus squamatus in four rivers and their branches in Jiangxi province, eastern China during two wintering seasons, from November to December, January to February from in 2007 and 2008. The results indicated that the main behaviors of M. squamatus included foraging, swimming, washing feather, resting state, sleeping, playing, flying and observing. For those behaviors, foraging, swimming, preening and resting occurred with obvious rhythm, however, feeding behavior took on reverse rhythm by comparing with resting. The behaviors of sleeping, flying, playing and observing occurred without obvious rhythm. Peaks of feeding behavior took place at 7:00-8:00 A.M,10:00-11:00 A.M and 12:00-13:00 P.M., and with an interval about 2.3 h between two peaks. The species feed more frequently in forenoon than afternoon. The frequencies of sleeping and resting in afternoon were significant higher than that in forenoon, and took on a fluctuated trait. The low frequency of sleeping and resting corresponded with three feeding peak. The time that the species spent on different types of behaviors was as follows: feeding (46%), swimming (23%), washing feather (9%), resting (8%), sleep (8%), flying (4%), playing (2%), and observing (0.5%). M. squamatus spent most time on feeding to accumulate energy during wintering period. The time that the species spent on feeding was negatively correlated with that on sleep (R = -0.73, df =8, P＜0.05), but positively correlated with that on flying (R = 0.70, df =8, P＜0.05), and time spent on preening was positively correlated with that on resting (R = 0.88, df =8, P < 0.01). No significant correlation relationships were detected for other behaviors.