Objective To study the effect of stair ascent on insert wear of total knee replacement (TKA) by finite element model, which is of great theoretical and practical significance for improvement of wear evaluation method and guidance of design of artificial knee joint prosthesis. Method A finite element analysis model of TKR wear based on Archard’s law was established and validated. The model was applied with loads under normal level walking (ISO14243) and stair ascent, respectively, to compare and analyze the influence of stair ascent on TKR wear. Results The predicted wear during level walking was consistent with experimental results reported in the literature. The volumetric wear rate during stair ascent was 37.10 mm3 per million cycles (MC), which was significantly higher than that during level walking (16.94 mm3/MC). The linear wear during stair ascent was significantly higher than that during level walking as well. Wear during stair ascent was mainly distributed in the backward area of medial platform, which was obviously different from that during level walking. Conclusions As a common daily activity with high loads and high flexion angles, stair ascent contributes an important part in TKR wear, and more attention should be paid to the testing and evaluation of TKR wear.