The method of improving image spatial resolution of the optical instruments with linear sensors in the three-axis body-stabilized platform was proposed by changing the sensors' relative positions as well as increasing the over-sampling ratio in some degrees. The basic iterative algorithm and the error spreading induced by the method were quantitively analyzed, and the certain relationship between the image spatial resolution and the image SNR was also presented. The technological feasibility of the method was proved by the patent technology of SPOT-5 HRG. This technology can been applied in the polar-stationary satellite platform under the current conditions.