A model for CaCO₃ eluviation and deposition processes in arid area soils called CAEDP, was developed based on mechanisms of chemical thermodynamic process and CaCO₃ deposition process in soil profile, and using other experiences in modeling for reference. The model was validated in the north west Shanxi Province, a typical semiarid area. The results showed that the model simulated the processes of CaCO₃ eluviation and deposition and the pH value in arid area soils realistically, using only a few readily avaible inputs, such as mean monthly temperature, crop growth season,soil water flux, and so on. The model can be used for quantitatively evaluating the effects of factors including climate, biota, topography,parent material, time and human activity on CaCO₃ deposition in soil profile, a relatively slow process in soil development. And the model can also be used for quantitative studies on soil change and global change.