Objective To make finite element analysis on a novel trapezoid sleeve combined with prosthesis stem by different length (90, 105, 20, 135 mm) and shapes (straight and curved stem), and study the differences in their primary stability. Methods The finite element model of femur-sleeve-prosthesis was established, the contact mode was set as face-to-face contact, and the micromotion of femur-sleeve-prosthesis stem was studied by simulating the loading conditions of standing on one foot and fast walking in physiological activities. Results The micromotion of trapezoid sleeve combined with straight stem was larger than that of curved stem during standing on one foot and fast walking. The maximum and average micromotion reached the peak when the length of prosthesis stem was 120 mm. During standing on one foot and fast walking, the average micromotion of trapezoid sleeve combined with straight stem was ( 67. 7± 43. 5) μm and ( 64. 1± 59. 2) μm, and the maximum micromotion was 121 μm and 146 μm. The micromotion around the trapezoidal sleeve remained constant as the length and shapes of prosthetic stem changed. Conclusions The trapezoidal sleeve combined with curved stem is superior to that with the straight stem. When the length of prosthetic stem is 90 mm, the optimal primary stability can be maintained.