Objective To develop a double-gasbag weight loss equipment based on body weight support treadmill training (BWSTT)，and analyze the reasonability of the structure design. Methods The mathematical model of double gasbags in the process of air inflation was established, and the 3D model of double gasbags was established and meshed using Gambit; the analog computation for gas flow of the gasbag was conducted using Fluent; normal subjects with body weight below 80 kg were selected for clinical experiments based on designing and roughing of the prototype. Results The inflation time of double gasbags was 16.9 s and the maximum weight loss percentage was 90%; the pressure inside double gasbags was 2 kPa, and the relationship between the weight loss percentage and inside pressure of the gasbag was obtained by clinical experiments, which verified the reasonability of the gasbag structure. Conclusions The double-gasbag structure can meet the requirements of weigh loss training, which provides an effective weight loss support method and a feasible structural design for patients with lower limb dysfunction during rehabilitation training.