In competitive market, the preservation of an organization depends on improvement in customer satisfaction with organization's products and services. The organizations attempt to increase customer satisfaction index by creating and implementing some projects. Since the implementation of projects requires cost and time, it is necessary to know about the effectiveness of a project before doing it. In addition, because of some resource limitations such as investment it is impossible to implement all projects simultaneously. Thus, it is necessary to prioritize the projects according to their effects on customer satisfaction index. In this paper, a model is presented to measure analytically the effect of projects on customer satisfaction index. In this model, first the organization's processes is analyzed to determine the relationship between customer satisfaction criteria and the processes. Then, factors affecting each process and consequently each criterion are determined by cause and effect diagram. Finally, the relationship between the effective factors and customer satisfaction index is established by a rule based expert system. Numerical example determines the effect of project entitled “designing and implementing a mechanized reception system” on customer satisfaction index. One can estimate that based on the model presented here, this project improves customer satisfaction index by 1.77%. Implementation of this project led to a rise of 1.9% in customer satisfaction index, the model has 6.8% deviation in practice. In general, verification of model shows a deviation of 6% to 8% between the model and practical results. This control reveals that the model is consistent with reality.