Abstract: Consumers hold certain stereotypes toward different groups, such as negative stereotypes for dissociative groups. Enterprises are not able to control the identities and behaviors of the brand users. If people from target consumers’ dissociative groups purchase and use the brand, will the target consumers be influenced by the situation? Based on the theory of stereotype and dual-system process model, this research explores the role of information processing approach in weakening dissociative group effect, and also discusses the mediating and moderation mechanisms of the relationship. The research verifies the hypothesis through five experiments: Experiment 1 confirms the negative effects of dissociative groups; experiment 2a and 2b find that mechanism of dissociative group effect lies in self-identity threat; by manipulating participants’ information processing approach, experiment 3 tests its effect on self-identity threat, thus dissociative group effect. Experiment 4 tests the moderating effect of self-affirmation. The results show that when consumers are primed to process information in an analytic way, they are less likely to depend on stereotypes in decision-making, thus the effect of dissociative group is attenuated. Self-identity threat plays a mediating role in the relationship. When consumers are self-affirmed, they are not vulnerable to the negative effect of dissociative groups. This research enriches the theoretical researches on dissociative groups and self-identity threat.