Tight interference fits are extensively applied in machine tool and industry, as it can provide stable bearing capacity in an efficient way. However, in most of proposed models for investigating the load bearing characteristics of interference fits, it is not common to consider roughness and form defects together. It is limited to describe interference fits of simple parts and investigate the effects of form defects approximately. The objective of this study is to present a feasible method to investigate the effects of form defects on the load bearing characteristics of interference fits of shaft and bush. The analytical method is established based on thick-walled cylinder theory and the experimental data on the joint surface. It takes both roughness and form defects into account, and predicts the load bearing characteristics under different parameters of form defects, such as the period and amplitude. The results show that the distribution of contact pressure of joint surface depends on the different parameters of form defects. Furthermore, as the amplitude of form defects decreases, the effects on bearing capacity of interference fits also decrease gradually.