The choice of the imaging focusing criterion function is the key of high-quality image acquiring in auto image measurement. The performances of several digital image processing methods used for autofocusing criterion are given. The focusing evaluation functions are compared and analyzed quantitatively through experiments in the aspects of calculation speed, unique value, precision and sensitivity. The results show that gradient square algorithm, Laplacian algorithm and second order gradient square algorithm have good behavior at the unique value and the sensitivity; and that both Robert algorithm and gradient mode algorithm have good behavior at the stability and calculation speed. These analysis results of image focusing criterion functions are useful for autofocusing in the automatic image measurement application.