Based on the LFM(Linear Frequency Modulation) signal and the principle of the heterodyne, the expression on the output of the heterodyne detection in synthetic aperture ladar was induced in detail with the considerations of phase error. Combining with the reference channel design and phase compensation algorithm, the influence of reference channel design on single point object image had been analyzed by simulation. Some error analysis concerning the compensation algorithm with sharpen function had been given by researching the physical meaning of sharpen function. Finally, the application scope of the phase compensation algorithm with sharpening function had been given out, and some problems to realize high quality synthetic aperture laser radar imaging had been pointed out in these paper.