<p>Major public health emergencies pose significant challenges to government–citizen cooperation and crisis governance. Against this backdrop, this study examines how citizens’ risk perception is associated with coproduction behavior, focusing on the mediating role of trust in government and the moderating role of positive emotion orientation. Using survey data collected in China during the COVID-19 pandemic, this study develops and tests a moderated mediation model grounded in risk perception theory, emotional cognition theory, and the cognition-emotion-behavior framework. The results indicate that risk perception has a positive impact on citizens’ coproduction behavior, and indirectly affects coproduction through the mediating role of trust in government. In addition, it was found that positive emotion orientation plays a moderating role between trust in government and coproduction behavior, enhancing the overall mediating mechanism. This study expands the understanding of the relationship between risk perception and citizens’ coproduction behavior in major emergencies, and provides practical insights for promoting citizens’ coproduction behavior. It also provides a theoretical basis for the government to innovate the emergency management of major public health emergencies and improve the ability of emergency management.</p>