An automatic defocus compensation method for human eye Hartmann-Shark (HS) wave-front aberrometer is proposed. According to the analysis of different geometric features of HS light spots during focalizing process, estimation algorithm is constructed to remove large-scale defocus amount, and then the residual high-order ocular aberrations can be measured by aberrometer successfully. Experimental results proved that the method has good robustness to control noise and can achieve accurate automatic defocus compensation from ocular aberrations, which is very useful method to human eye HS wave-front aberrometer.