Abstract: Previous researchers have considered“perpetual imprisonment” in the Qing dynasty a eculiar result of the autumn assizes and court assizes, but this phenomenon has not received the full attention it has deserved. An examination of textual evidence and a survey of the practice reveals that it appeared first in the ianlong Period and reached its peak in the Jiaqing and Daoguang Periods. Over time there were two types of perpetual imprisonment. There was institutional and expedient perpetual imprisonment. Due to its flexible, punitive and hierarchical characteristics, perpetual imprisonment played a role that was unlike any other means of punishment. The practice of perpetual imprisonment was an example of the imperial commitment to balancing circumstances and law in doubtful cases, and crime prevention that reflected perpetual imprisonment’s penal nature.