[Purpose/significance] The network public opinion of major emergencies is very easy to cause public panic and bring a series of social problems. It is of great practical significance to comprehensively analyze the multiple causal paths that trigger the network public opinion of major emergencies.[Method/process] Using the method of integration of NCA and fsQCA, this paper selects 90 Internet public opinion events related to COVID-19 from 2020 to 2022 as re? search materials. Based on the perspective of PSR framework, it explores the influence mechanism of the factor configu? ration of seven antecedents of public opinion aggregation, communication channels, authoritative media, public atten? tion, event heat, time span and harm degree on the trigger of network public opinion in major emergencies.[Result/con? clusion] It is found that a single factor does not constitute a necessary condition for the triggering mechanism of net? work public opinion in major emergencies. The role of single factor in triggering network public opinion in major emer? gencies is limited. This paper digs out the conditional configuration of the trigger mechanism of network public opinion in 9 major emergencies. Event heat, authoritative media and public attention are the core conditions. This paper summa? rizes three theoretical driving modes of the trigger mechanism of network public opinion in major emergencies, namely event driven, authority led and public appeal. This paper aims to improve the accuracy and efficiency of the network public opinion guidance of the government's major emergencies and improve the government's credibility.