Low-cost GPS/INS integration system is the idea positioning part of open-pit mine transport truck monitoring and dispatching system.However,the sensitivity of low-cost INS is not enough to finish the initial alignment in statics base before navigation.Aiming at this problem,this paper presents a generic inertial navigationsystem in-motion alignment error propagation model which does not rely on small misalignment angles assumption.The model is presented in the ECEF frame approach and is very suit to implement the in-motion alignment with GPS aided.The simplified Cubature Kalman filter is proposed to implement the non-linear error model.An open-pit mine transport truck navigation test is simulated with an actual vehicle test data.It is indicated that low-cost INS with GPS aided can finish the in-motion alignment under the large misalignment angle assumption and the proposed model is correct and practicable.