The algorithms of angle read-out were designed for imaging-type absolute angular encoder on the basis of its working principle. The algorithms for image pretreatment and angular measurement were illuminated separately in this paper. Firstly, the image of code disc was pretreated by graying, smoothing and binarizing successively to obtain the proper binarized signals. Then, the coarse code and subdivision code, of which the angle is consisted, were read out along the disc’s radial direction and tangential direction, separately. In the end, the feasibility and validity of algorithms were testified in the experiment.