The aim of this research is to determine and to assess the effective factors on customer loyalty, concerning the internet-purchase of products and services of Tehran tourism agencies. For this purpose, the standardized questionnaire was distributed among on-line internet customers of Tehran tourism agencies and finally 384 questionnaires were applied in analyzing the research hypotheses. The data obtained from customers were analyzed using confirmatory factor analysis technique and the structural equations modeling (SEM). The findings of the research with regard to the proposed model and its nine hypotheses from the highest to lowest route coefficients and hypothesis confirmation are respectively: the effect of customer loyalty with the route coefficient of 0.559; the effect of search capability with the route coefficient of 0.481; the effect of satisfaction on customer trust with the route coefficient of 0.388; the effect of transaction cost on customer satisfaction with the route coefficient of 0.321; the effect of search capability on customer trust with the route coefficient of 0.292; the effect of trust on customer loyalty with the route coefficient of 0.184; the effect of the perceived security on customer satisfaction with the route coefficient of 0.159. The above seven hypotheses have been confirmed and the effect perceived security effect on customer trust and the effect of transaction cost on customer trust with the route coefficient of 0.018 were finally rejected.