With the increasing prevalence of online shopping, many companies have added "personalized recommendation" modules on their websites to collect customers' click-stream data in real time and conduct relevant analysis, which will both assist the decision-making of the web owners and enrich the interactive experience of the customers. A website with more personalized recommender system allows users to experience others as psychologically present being, conveys a feeling of human warmth and sociability which is believed critical for the formation of consumers' trust towards online stores. In this study, a laboratory experiment was conducted to empirically examine the effects of the level of perceived personalization on consumers' trusting beliefs towards online store. The result also demonstrated that the perception of social presence can partially mediate the effect of perceived personalization on consumer's trusting beliefs.