Objective To perform finite element analysis on a type of newly designed total knee prosthesis, and investigate the influence from changing twist angle of the lateral condyle surface on mechanical environment of the knee joint. Methods Based on CT measurement data from a volunteer, 3 artificial knee prostheses with the same medial condyle were established. In Model 1, the twist angle of lateral condyle surface was 0°, while 10° and 20° in Model 2 and Model 3, respectively. The prosthesis models were imported into finite element software and applied with gait cycle data to simulate the motion of knee prosthesis during the gait cycle. The simulated stress results in the knee joint were then compared with the calculated results, which were obtained from theoretical formula of contact mechanics. Results The maximum stress of 3 models appeared at 13% of the gait cycle, when the axial force (2.6 kN) was also the maximum. The maximum stresses of medial and lateral condyle in Model 1, Model 2 and Model 3 were 35.5 and 30.6 MPa, 38.4 and 32.6 MPa, 38.3 and 43.1 MPa, respectively. The stress curves of Model 2 and Model 3 during the gait cycle were relatively smooth compared with those of Model 1. The simulated stress trend was basically similar to the theoretical calculation, except at a few moments in the gait cycle. Conclusions The mechanical environment of the total knee prosthesis can be improved by twist angle of the lateral condyle surface. This newly designed prosthesis can preserve implants from abrupt change of the stress during the gait cycle and prolong the service life of prostheses.