Utilizing 336 documents of administrative punishment decisions on fabricating COVID-19 rumors in Zhejiang province between December 2019 and December 2022, this article explores the effects of three sets of factors on the severity of administrative punishment. Empirical results suggest that administrative punishment for COVID-19 rumors is an ad hoc administrative measure only utilized in a state of emergency when the Chinese government implemented the “dynamic zero-case” policy. While it did not directly contravene existing Chinese laws, such a type of punishment practice represented the expansive trend of administrative punishment power. It caused tension with the current legal system. The expansion of administrative power manifested through the broadened scope of punishable false speech, lowered criteria of public order disruption, and lowered punishable criteria of offenders’ intent. Given that the Chinese society (as any other societies) periodically enters a state of emergency, it is necessary to consider how to maintain a dynamic balance between the abnormal exercise of administrative power and the protection of individual’s basic rights when the emergency reappears. This article advances the understanding of the dynamics surrounding administrative punishment for rumors and furnishes policy and legal recommendations for employing administrative measures in rumor control during national emergencies.