This paper describes the development of a fuzzy decision support system (FDSS) for the assessment of risk in E-commerce (EC) development. A Web-based prototype FDSS is suggested to assist EC project managers in identifying potential EC risk factors and the corresponding project risks. A risk analysis model for EC development using a fuzzy set approach is proposed and incorporated into the FDSS. For running the fuzzy set approach, the researchers use MATLAB software. The research methodology includes these stages: At first, identifying the factors effect on the development of the E-commerce with the help of experts; secondly, defining the suitable membership function for each factor. There are three layers in the fuzzy system that every layers output is input for next layer. Then, the system calculates the final risk through SUGENO inference engine for E-commerce. Indeed the suggested architecture for the model with the help of experts is presented in this paper.