Abstract: Many operation events of nuclear power plant such as the Fukushima nuclear accident have exposed the common problems of imperfect and unclear collective decision-making mechanism in emergency situations such as the transient/accident, and the post-event disposal often focuses on solving technical problems, ignoring the design of collective decision-making process that causes technical problems. This paper deeply analyzes the responsibilities of the members of the on-duty team in the emergency state of nuclear power plant, the requirements, contents, process and mechanism of collective decision-making,and designs a specific collective decision-making process according to the new requirements brought by the introduction of the automatic diagnosis system into HPR1000 to the operation team decision-making. The decision-making process integrates the operation experience and the defense-in-depth concept, organically combines the independence and collectivity of team members, and can improve the overall ability, efficiency and quality of decision-making of the operation team, and minimize or avoid decision-making mistakes.