Safety is one of the most significant considerations in the civil aircraft design. Based on analysis of the independence between elements or events, Common Mode Analysis is also used to guarantee the safety of the design object. The procedure of Common Mode Analysis is introduced in this paper, listing the common failure sources and its failure modes in detail. Furthermore, the “AND-GATE冶method and “SHORT-CUT冶method of the Common Mode Analysis are presented. By an real example of a pressurized compartment door, two methods are analyzed in a mechanism system,which were used for Common Mode Analysis. And the relevant conclusions are given.