Abstract: he ballistic-lifting reentry vehicle usually is a revolution bodywith its off-axis mass center.This vehicle uses parachute as a principal deceleration means in the last stage of its returning trip to the ground.A study of the motion stability of the combined system that consists of a revolution body with itsoff-axis mass center and a parachute is of practical significance in engineering.Asa preliminary discussion,the system's stability around its equilibrium is examinedand the criteria of the motion stability are given with rigid body model ofparachute assumed and based upon the system's equation of plane motion.