Multi-aperture coherent imaging technology can achieve high resolution imaging through sub-aperture coherent synthesizing. One of the key problems is co-phasing errors between sub-apertures. Typical errors include high-order aberrations within each sub-aperture and orientation errors between sub-apertures. The orientation errors include shift and rotation errors. Phase errors are corrected based on the image sharpness optimization. Simulations for three sub-apertures coherent systems are carried out. Results show that sharpness optimization based on stochastic parallel algorithms can correct shift phase errors of intra-apertures and inter-apertures pretty well. However the stochastic parallel algorithms don’t suit for rotational errors of inter-apertures. Through computing the sharpness of synthesized images within a certain rotating angles and searching the extreme value, rotational angle errors of inter-apertures can be well extracted.