In this paper, a method for axis to plane in random direction perpendicularity error evaluation based on new generation GPS is proposed. On the basis of a comprehensive study about the definition and measurement method of perpendicularity error, the evaluation model based on the minimum zone conditions is established. Datum plane is transformed to coordinate plane through transition matrix, so the perpendicularity error of measured element to datum plane can be transformed to that of measured element to coordinate plane. The evaluation model is simplified. Example shows that the perpendicularity error of axis to plane can be evaluated accurately and effectively.