Objective To investigate from biomechanics the effect of acetabular coverage level on the osteoarthritis secondary affected by dysplasia. Methods The three dimensional finite element hip models of normal, dysplastic and over-covered were established to observe the regularity of stress distribution and the areas of stress concentration in dysplastic hip by nonlinear contact analysis. Results It was found that the pressure concentrated at the superior dome in all models, and some redundant high pressure occurred at the area near posterior-superior rim only in the dysplastic hip models. With the decreasing of the CE angle, contact pressure and peak stress increased remarkably, and the contact area decreased as well. But the changes of the pressure distribution and contact pressure were not significant when the CE angle was larger than 30°. Conclusion The biomechanics changes owing to decreasing of acetabular coverage level plays an important role in the osteoarthritis secondary affected by dysplasia.