This paper makes an investigation on the algorithm of reconstructing a 3-dimentional CAD model from 2-dimentional photos. By a set of points picked on an object's 2-dimentional photos taken in different direction and position, the movement parameters of the camera and the 3-dimentional geometric information and CAD model of the object can be calculated with the algorithm. The algorithm makes sufficient considerations on the constraints of manufacturablity in CAD modelling, is accurate and robust, and will be useful in the fields of reverse engineering, computer vision and robots.