In order to research the relationship characteristic between the interference fit value and stress value of wheel-axle, the traditional contact stress formula based on the mechanics of elasticity and the finite element method was applied. Graphs according to the stress data of 11 picked axle sections and corresponding interference fit value was drawn out, and the linear correlation coefficient r by numerical analysis method was calculated. The analysis results showed that there was a good linear correlation between the calculated stress value and the interference fit value of wheet-axle, and the stress value of the wheel-axle mating area on the axle was influenced greatly and the other areas were less influenced by the interference fit value.