Load identification method is applied to force measurements in impulse combustion facilities. The dynamic model of the testing system is derived using substructure synthesis method. Then, the differential equations are discretized to establish the linear relationship between the outputs of balance and the dynamic forces history acting on the aircraft model. A hybrid regularization method which combines the Tikhonov regularization and subspace projection methods is proposed to solve the load identification problem. The hybrid method converts the ill-conditioned large scale problem into a well-posed small scale problem which can be solved easily. A new method is proposed to determine the size of the projection subspace. The L-curve criteria is employed to search the optimal regularization parameter of the dimensional-reduced problem. The accuracy of the structural dynamic modeling method and the effective and stability of the load deification method are validated by a numerical example.