In order to obtain more accurate dynamic characteristics of parachute, an improved dynamic model is deduced according to the momentum and the momentum moment theorems of the particle system. On the basis of the model, the terminal descent stage of a cruciform parachute is coded. The change processes of the velocity and attitude angles of the parachute a nd payload are obtained. The simulation results are consistent with the airdrop test results. This model is easy to program and can obtain more accurate oscillation frequency of the parachute velocity and attitude angles. Therefore, the model is a useful supplement to the conventional parachute dynamic model.