This paper presents a mechanical jumping leg with the capability of jumping,retracting the leg in the air and adjusting the energy of spring.For the purpose of reducing the weight and the energy consumption,the jumping leg is actuated by a single motor.The 5-bar linkage is adopted as the main part of the leg including the foot and the tarsometatarsal joint to enhance the stability during jumping and landing.The key motion of each phase in the whole jump is analyzed by simulation.Experiments are implemented on the jumping leg robot,and the result demonstrates that it has good capability of jumping,shows high jumping efficiency,and can retract the leg in the air for landing steadily.The mechanical leg will be applied to the design of jumping frog robot as hindlimb.