In order to better understand the overwintering behavior patterns and sex differences of Aythya baeri and provide a scientific theoretical reference for the future protection and management of Aythya baeri and its habitat resource. From November to December 2018, we observed and analyzed the overwintering behavior patterns and gender differences of Aythya baeri in Henan Minquan National Wetland Park by methods of fixed-point observation and scanning sampling. In total of 158 Baer's Pochards were recorded during the observation period, and more than 10% of the world population. The results showed that (1) in the Minquan Wetland Park, the overwintering behavior time allocation of Aythya baeri was mainly composed of resting, foraging and sport, followed by maintain and flying. There existed significantly positive correlation between sports behavior and foraging behavior, maintaining behavior and social behavior, and also significantly positive correlation between maintaining behavior and social behavior. While, there was significantly negative correlation between resting behavior and maintaining behavior, sports behavior, social behavior, and significant negative correlation between flight behavior and foraging behavior, resting behavior, maintaining behavior. (2) The resting behavior had the characteristics of full-time high time allocation, and there were no peak and valley periods. The foraging behavior (peak period is 10:30-11:30 and 13:30-14:30; valley period is 11:30-12:30 and 14:30-15:30) and flight behavior (peak period is 11:30-12:30 and 14:30-15:30; valley period is 10:30-11:30, 13:30-14:30, and 15:30-16:30) had obvious alternating peak rhythm. (3) It existed obvious differences about time allocation of overwintering behaviors between different genders, among which rest, foraging and sport were the main behaviors of male Aythya baeri (more than 70%), while the main behaviors of female Aythya baeri were movement, flight and foraging (nearly 70%). There were significant differences in the time allocation of rest, maintaining, sport, and flight between male and female. The time allocation of rest and maintaining of male was significantly higher than that of female, while the time allocation of sport and flight was significantly lower than that of female. (4) In wintering behavioral activities rhythm of Aythya baeri with different genders, except for flight behavior, the other behaviors were different in behavioral peak and valley rhythm. Further analysis showed that the overwintering behavior model of Aythya baeri in Minquan Wetland Park conforms to the behavioral investment and return principle from energy theory, and there were gender differences in the behavior time allocation and behavior rhythm.