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 elective course were enrolled as the research objects at Shanghai Institute of Commerce and Foreign Languages from September to December 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 technology and tactical training courses, emphasizing the fun of sports activities, and drawing on various forms of sports games when designing 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/m 2], 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 physical education mode based on constructivism can alleviate learning burnout, improve mental health and optimize body shape of college 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.