In this paper, we propose a subaperture imaging algorithm that can be used flexibly to divide the aperture. In the implementation of the algorithm, firstly full aperture data is divided into the subapertures in azimuth time domain according to the needs of motion compensation or computing ability. Then each subaperture separately is operated by range migration correction, range compression, phase compensation and so on. Then the processed subaperture data are spliced into full aperture data in accordance with the division sequence. Finally, the image of the whole scene is obtained by the azimuth matched filtering for the processed full aperture data. Compared to the traditional subaperture imaging algorithms, the algorithm in this paper has the following two characteristics:1, The operation of the coherent and image splicing is not needed, and the calculation is reduced. 2, The full aperture can be divided into the subapertures.