On-line trading or Internet Commerce restoring to ECommerce systems are gradually replacing the traditional commerce activities. Internet users must have reasonable faith on the underlying systems before comfortably using it, To convince users to confidently enjoy the benefits that Internet and E-commerce systems can bring, an E-commerce system needs to be trustful and convincing to the users. In the paper, we proposed a computational model on which the E-commerce system can be developed, and the trust level will be introduced and assessed based on users attitudes, opinions and motivations, and provide some insight for the customers of Internet commerce. The model has two features: to assess the trust level of existing Ecommerce systems, and to recommend the E-Retailers how to improve the trust level. Based on the model, a prototype system of assessing trust level of E-commerce system has been designed. Online based e-EI system has demonstrated the computational model is feasible an...