Objective  Based on the sitting position, this paper designes a system for lower limb rehabilitation training, which can help patients with hip, knee and ankle joints rehabilitation. Methods Firstly, the whole structure of sitting lower limb rehabilitation training system was designed; and the Software SolidWorks was used for the whole structure of 3D modeling.Then，we used the finite element analysis software to analyze the deformation and strength check of the main bearing parts. Finally，the sample machine was debugged to verify the feasibility and rationality of the design. Results The system included a movable chair, two external skeletal mechanical legs, a distance adjustment device of hip, and an electric cabinet.Seat support’s maximum equivalent stress and the maximum deformation was 5.2315MPa and 0.0128mm. Mobile guide’s rod maximum equivalent stress and biggest deformation was 204.59MPa and 1.72mm. Ankle part’s maximum equivalent stress and deformation was 97.326MPa and 0.62mm. The training system could meet the height within 155-190cm patients. When the mechanical leg knee joint moved to the maximum and minimum limit angle, the reliability ICC value was 0.823 and 0.895. When the mechanical ankle moved to dorsiflexion and toe ultimate flexion angle, the reliability ICC value was 0.861 and 0.833. Conclusions   The strength and the deformation of the main stress components can meet the requirements. This training system can reach the range of preconcerted actions of three joints, lead patients with lower limb dysfunction to practice many types of lower limbs rehabilitation training, to have good feasibility and rationality.