In the context of big data, the internet celebrity economic marketing model has gradually become one of the mainstream online marketing models. Internet celebrities use their special influence and characteristics of the times to bring revolutionary changes to product promotion. This phenomenon carries more economic value and has significant social impact. At the same time, the development of the Internet celebrity economy has triggered concerns that irrational consumer behaviour may disrupt the e-commerce market. This paper investigates the influence of the Internet celebrity economy on consumers’ irrational purchase behaviour in this environment. To do so, the K-means clustering method is utilized to collect data on both internet celebrity economies and consumers’ irrational buying behaviour. The study develops a research model with the independent variables of internet celebrities’ professional degree, credibility, and fan attraction, and the dependent variable of consumers’ buying behaviour, with consumers’ buying sentiment serving as an intermediary variable. The empirical analysis demonstrates that the Internet celebrity economy significantly impacts consumers’ irrational purchase behaviour, with higher levels of professionalism, credibility, and fan attraction among internet celebrities associated with greater likelihoods of irrational consumer purchasing. Based on these findings, two strategies are proposed to mitigate irrational purchasing behaviour: improving the professional quality of internet celebrities and promoting rational consumer buying practices.