In this research for the first time the moderating role of user knowledge in designing a web interface and electronic trust (e-truet) was studied. To this end, about 700 electronic questionnaire was sent to the target population of the study which consisted of faithful users of forum Arirangfa. 240 questionnaires were completed. Accepted questionnaires were analyzed through structural equations and partial least squares method and Smart-PLS 2.0 software. The results of the analysis of data indicated that: 1) the model was a robust theoretical model for predicting electronics' trust through design of web interface. 2) According to user view, graphic design of website are not related to e-Trust. 3) Among dimensions of web design, structure design has the greatest impact on users' trust on the website. 4) The level of user knowledge can not moderate the relartion between design dimentions of website and e-trust.