The landing dynamics equations were educed with the establishment of two-mass equivalent model and the supplementary equations under the sideslip landing. An aircraft model with flexible fuselage using virtual prototype was applied basing on the mathematical models of landing gear in landing and ADAMS/Aircraft version. A simulation of dynamic response under sideslip landing has been analyzed. Simulation results show that the flexible fuselage leads to the increase of returning roll torque and the decrease of the tires- sideslip. It leads to symmetrical landing fast. The flexible fuselage can absorb and dissipate the landing shock energy. The comfort of airplane can be improved and the weight of landing gear can be decreased. Then the foundation to ameliorate landing gear has been laid.