Abstract: With the combination of CCD imaging unit and traditional multiimage camera to measure far-field distribution of laser output, the reconstruction algorithm for focal spot of high power solid state laser output was described. The geometric cores of these focal spots was abstracted to center these spots by virtue of edge computational kernel applied in the field of image processing, nesting algorithm for focal spot reconstruction is put forward. It can precisely center these spots even if they are saturated partially and instantly reconstruct original focal spot, which makes it feasible to provide realtime data for laser control.