In order to meet the functional requirements and the safety requirements of airworthiness regulations, there are many types of mechanisms in the cabin door of civil aircraft. The quality of mechanism design is directly related to the performance of door. This paper introduces the composition of the cabin door mechanism. Based on the requirements of the latest airworthiness regulations, the design requirements and key point of security mechanism design were analyzed, and the monitoring logic requirements of latch, lock and pressurization prevent mechanism were extracted. According to the design requirements of security mechanism，taking mature aircraft as an example，the monitoring logic analysis method of door security mechanism is given.The state of the door latch, lock and pressurization prevention mechanism and the compliance of the safety monitoring logic were analyzed in the case of single failure of the transmission mechanism， and some suggestions on the design of mechanism motion sequence were given, which can provide a reference for the design of other types of cabin door safety mechanisms.