Objective To explore the effects of happy physical education based on constructivism on physical education learning burnout,body shape and mental health of college students,so as to provide a reference for the reform of physical education teaching in universities.Methods By using cluster sampling method,students from two teaching classes of the 2022 physical badminton e-lective course were enrolled as the research objects at Shanghai Institute of Commerce and Foreign Languages from September to De-cember 2022.They were randomly divided into experimental group(n=38)and control group(n=40)by drawing lots.The control group received routine physical education teaching for 16 weeks,with 2 class hours weekly and 45 minutes per class hour.While the experimental group was given happy physical education based on constructivism,with a teaching process of building a framework,independent exploration,collaborative learning,and effect evaluation.The idea was to integrate Happy Sports into badminton tech-nology and tactical training courses,emphasizing the fun of sports activities,and drawing on various forms of sports games when de-signing sports activities.Two groups of students were tested for body shape,surveyed with the Physical Education Learning Burnout Scale and Symptom Check List-90(SCL-90).The scores of Physical Education Learning Burnout Scale,body mass index(BMI),waist-to-hip ratio,body fat rate and SCL-90 were compared between the two groups by t-test,Chi-square test and Fisher's exact probability test.Results At the end of the semester,BMI[(21.58±1.59,22.30±1.46)kg/m2],waist-to-hip ratio(0.75±0.08,0.79±0.07)and body fat rate[(19.77±2.50)%,(21.02±2.46)%]in experimental group were lower than those in control group(t=-2.09,-2.35,-2.23,P<0.05).The scores of depression(15.10±3.92,17.24±4.18),improper behaviors(13.60±3.05,15.48± 3.52)and low sense of achievement(5.52±1.36,6.54±1.42)and total score of Physical Education Learning Burnout Scale(34.22± 7.55,39.26±7.86)in experimental group were lower than those in control group(t=-2.33,-2.52,-3.24,-2.89,P<0.05).The scores of somatization(16.27±3.75,18.57±4.12),interpersonal sensitivity(14.30±4.57,16.85±4.21),depression(17.02±3.89,19.36±4.28)and anxiety(12.68±3.96,15.32±3.87),and total scores of SCL-90(127.87±22.54,140.54±25.83)in experimental group were lower than those in control group(t=-2.57,-2.57,-2.52,-3.00,-2.30,P<0.05).Conclusions The happy physi-cal education mode based on constructivism can alleviate learning burnout,improve mental health and optimize body shape of col-lege students.Appropriate reforms should be made to the teaching mode of physical education in universities to promote the physical and mental health development of college students.