Abstract: Traditional exoskeleton robots are mostly of rigid structures, and have a lot of limitations such as large self weight, poor flexibility and poor wearing comfort. To solve these problems, a lightweight flexible lower-limb exoskeleton is designed. The flexible assistance to ankle joint is realized by Bowden rope device and spring device. The "single wheel and double slot" winding coil of the drive system can drive the legs by a single motor, and its stability is verified by finite element analysis. For the exoskeleton control strategy, a motor angle and rotation speed based PID (proportional-integral-differential) control and an ankle joint torque based PID control are put forward based on the traditional three-loop PID feedback control of motor system, and their feasibility is simulated and verified through Simulink and Simscape tools. Finally, an exoskeleton prototype of only 3.095 kg is built and the performance experiment is carried out. Under the experimental conditions set in this paper, the metabolism of human body decreases by 15% when wearing the exoskeleton, which demonstrates the rationality of the exoskeleton design, and also shows that the exoskeleton has better assistance effect than the traditional ones.