Abstract: Although the parachute is widely used in deceleration system, it's seldom mentioned the establishment of moving equation and especially the added mass. It's the main reason to give a concrete description of the added mass in parachute, from introduction of concept, and application in equation, to determination and rule of numerical value, and analysis of parachute stability. Because parachute is light, flexible and blunt, its added mass is determined by many factors, which rule could be found from experiment data. And from root locus analysis, its effectin stable dropping of parachute is important.