In this paper, the authors describe 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.