Objective To improve the clinical application of body weight support treadmill training (BWSTT) robot and develop a practical way for promoting the rehabilitation robot, this paper proposes a design plan of lower limb robot with flexible structure, simple operation, and strong practicality in allusion to the weak clinical applicability of traditional BWSTT robot. Methods Based on methods of modular design and intensive design, the whole body of the robot was divided into several functional modules including wearable exoskeleton, weight loss training device, adaptive treadmill and suspension vest from the view of ergonomics, rehabilitation medicine, and mechanical design and so on. Meanwhile, an optimization analysis design was made for key parts of the robot through theoretical calculation and SolidWorks simulation. Results After the concrete manufacturing and clinical experiments, the feasibility and scientificity of the BWSTT robot design was validated. Conclusions This clinical application design can improve the practical application of BWSTT robot and also provide a reference for the wider use of the lower limb rehabilitation robot.