The paper presents a statistical model for static contact parameters of joint surfaces. The model is developed based on statistical analysis of surfaces topography, and the assumption that the transitions from fully elastic, through elastoplastic, to fully plastic deformation of an asperity are continuous. The nonlinear relationships between contact parameters and their influencing factors are simulated numerically under different distributions of asperity heights and plasticity indices. The results indicate that the modified exponential distribution is a good approximation to the Gaussian distribution. On the other hand, the estimates using the simple exponential distribution are 1 to 3 orders of magnitude larger than that of the Gaussian distribution. The contact parameters all increase as the mean separation between the two surfaces is decreased. In addition, the contact load and the contact stiffness increase with the plasticity index, but the changes of contact area are not significant.