The pose registration between 3D measured data and freeform surface design model is the key to complex surface machining and inspection. In order to realize fast and accurate surface registration, a method based on the maximum entropy principle was proposed. A unified mathematics model was developed based on the analyses of machining localization and the registration problem of quality evaluation of parts. The efficient numerical algorithm for the unified model was researched. Based on the maximum entropy principle, the registration problem established on the min max criterion was converted to a perturbed problem with the entropy function as the perturbation. As a result, the non differentiable object function is perfectly substituted with the maximum entropy function. This provides a possibility to improve the efficiency of solving registration problems. Experimental results about the allowance distribution and the error inspection show the validity and practicability of the method.