Social commerce, with its unique social attributes, has promoted the group-buying mode to become an important marketing tool. Based on the stimulus-organism-response (S-O-R) paradigm, this study constructs a research model of the impact of the social e-commerce platform Pinduoduo group-buying mode on impulse buying, and uses structural equation model (SEM) for empirical analysis. The research results show that under the group-buying mode: perceived price fairness and reciprocity have significant positive influence on satisfaction; source credibility and similarity have positive effects on trust. Trust is positively correlated with satisfaction. Trust significantly affects impulsive buying impulse, but satisfaction has no significant impact on impulsive buying impulse.