Abstract: The matching between parameters of ski-jump ramp and flying performance/quality of carrier-based aircraft was analyzed based on the dynamic process of force polygon and the effect of ski-jump ramp on the pitch rotation of aircraft, and the building-up mechanism of the angle of attack at the initial stage after aircraft leaving the ramp at low speed was demonstrated. The building-up of the angle of attack results from following three aspects: The ramp provides the aircraft a positive pitch rate, which increases the angle of attack; When the nose landing gear leaves the ramp and the main landing gears do not, pitch down moment is provided by the ramp reacting force upon the main landing gears, and the pitch rate is decreased; While the aircraft just leaves the ramp, the lift cannot balance the gravity, so the acceleration vector points forward and downward, the speed vector is deflexed, and the angle of attack is increased. Simulation on the multi-bodies dynamic system of carrier/aircraft/landing gears shows that the above analysis is reasonable.