The vehicle may be induced uncommanded oscillation by the disturbance of the gust, this phenomenon would increase the risk of the flight. To study the influence of forced pitching oscillation on rolling characteristics of a square cross section vehicle, the loose couple technique of rigid body dynamic equations and Navier-Stockes equations were developed, and then the steady rolling aerodynamic characteristics, free rolling characteristics and the effect of pitching oscillation at different frequencies on rolling characteristics of the aircraft were studied. The steady results showed that there was a critical attack angle about 13° existing in the free rolling motion, when the attack angle was lower than the critical attack angle, the vehicle was in rapid rolling motion, and when the attack angle was greater than the critical attack angle, the rolling motion was convergent. The results also showed that, the forced pitching oscillation would decrease the level of rolling static instability (stability) as the vehicle was static instable (stable), and increase the level of rolling dynamic stability no matter the vehicle was stable or instable. In the influence of high frequency pitching oscillation, the rolling motion can be convergent even if the vehicle was static instable.