A new type of lower limb prosthesis with MR damper and four-bar linkage was designed. Through Opensim simulation, the lower limb joint angle curve was obtained. In order to realize the joint motor tracking the joint angle curve, the joint angle curve was taken as the target trajectory curve, the joint motor experimental test platform was built combined LabVIEW and STM32, and the motion control of the joint motor of lower limb prosthesis was studied. The results show that the error between the actual trajectory of the electronic control joint and the target trajectory is less than 3.5 °, and the electronic control joint has good tracking effect on the target trajectory curve.