[Purpose/significance] In emergency situations, information search obstacles and information asymmetry lead to the obstruction of event information dissemination. Evaluating and analyzing the friction of online public opin⁃ion information in emergency situations, and providing reference theoretical tools for emergency management are of great significance for improving the government's public opinion governance capabilities. [Method/process] Based on the concept of information friction in information economics, an evaluation indicator system for online public opinion in⁃formation friction in the context of public events is constructed from two dimensions: information search obstacles and information asymmetry. Using the entropy weight method to evaluate and rank information friction in different thematic time periods, we compare online public opinion information friction based on the Kruskal Wallis non parametric test for different lifecycles and topic types. The effectiveness of emergency response is measured from a public perspective.The impact mechanism of information friction on emergency response effectiveness is revealed through correlation anal⁃
ysis. [Result/conclusion] This study establishes a quantitative standard for the friction of online public opinion infor⁃mation. Results find significant differences in information friction among different lifecycles and theme types, with high⁃er friction in the initiation and outbreak periods, and higher friction in the topics of investigation accountability and emotional expression. There is a significant negative correlation between information friction and the effectiveness of emergency response. Information search obstacles have a greater impact on the effectiveness of emergency response compared with information asymmetry. The findings provide suggestions for government departments to govern the dis⁃semination of online public opinion information during public events.