The projectile which works in a certain speed and altitude throws parachute-bomb system, and swing of parachute-bomb systems influence interception and impact angle and attack effect. Attitude swing of cross parachute-bomb system in balanced wind speed has been studied by test of vertical wind tunnel and unsteady numerical simulation. The constraint method of ‘pulling’ is presented in the test, and the shape and drag coefficient and swing frequency of parachute is obtained by way of the test. On this basis, the reason of parachute swing is further studied by three-dimensional unsteady numerical simulation. The results indicate that the computational drag coefficient and frequency of normal force coefficient (lateral force coefficient) is close to that of the experiment, and the flow around the parachute is unsteady. There are two vortices, whose directions are contrary and intensities vary alternately in the parachute. Moreover, there is the unsteady detached flow upon the parachute. The vortices relate with the unsteady detached flow. Aerodynamic coefficients change periodically. Thus, the attitude of the parachute-bomb system become unstable. The method of wind tunnel test and numerical simulation would be referenced in the design of similar parachute-bomb system. And the conclusion can provide a theoretical basis to optimize the parachute-bomb system.