Aiming at the problem of multi-difference aerial camera image detection accuracy, a multi-difference spatial filter parameter selection method is proposed. Firstly, the spatial filtering method and the automatic focusing based on the spatial filtering effect are introduced. Secondly, the implementation process of multi-difference filter focusing method is introduced, and the relationship between the selection of filter parameters and the focusing accuracy as well as the sensitivity is analyzed from the view of the power spectrum of filter output signal. Finally, the dynamic imaging experiment is designed, and the location images are collected under the typical guide speed of 532mm/s. Different filter parameters are selected to detect the image plane for 20 times, and the focusing effect is compared with that of the traditional image-focusing operator. The results show that the parameters selected by the multi-difference filtering method in this paper improve the focusing accuracy by 18% compared with the Brenner algorithm. And the maximum error of the focusing system is 3392 m, less than the allowable error of the optical system（768 m）, which meets the practical requirements.