To solve the problems of discontinuous disturbance，uncertainties，actuator dead zone and composite saturated nonlinearity of the variable swept-wing Near Space Vehicle (NSV)，an adaptive multi-model switching sliding mode attitude controller based on sliding mode disturbance observer and an auxiliary system is proposed. Firstly，a nonlinear multi-model switching system under disturbance and actuator composite nonlinearity is established. Then，as for the uncertainties and the discontinuous disturbance，a mode-synchronized switching sliding mode disturbance observer is designed to estimate composite disturbance. As for the dead zone and composite saturated nonlinearity of the actuator，the dead zone right inversion function is introduced to equivalently transform the composite nonlinearity into a new saturation stage，and an auxiliary anti-saturation system is constructed to deal with it. Next，an adaptive multi-model switching sliding mode controller for attitude tracking is designed based on backstepping. Different from conventional sliding mode control，different sliding surfaces are designed for each subsystem of the switching system，and common coordinate transformation is realized through a transitional sliding surface. The Lyapunov theory and the average dwelling time theory are used to prove the stability of the closed-loop switching system. Finally，the effectiveness and superiority of the proposed method are verified by comparing it with the conventional sliding mode control.