Abstract: The evaluation of microarray optical components is a new task in the field of optical test. The improved Foucault knifeedge test technology has many advantages as real time, digital, precision, etc. This paper introduces the principle and the experimental setup of knifeedge digital test of the surface characterization of micromirror array, and describes the key steps in processing the images of the micromirrors recorded by the CCD detector as: (1)precisely determine the knifeedge position correspond to the darkness threshold of every pixel; (2)determine the slope error of the surface area correspond to the given pixels; (3)reconstruct the examined surface. Furthermore, it also presents some elementary experimental results that the surface error is up to nm level.