We propose a new grating model building method by the inverse-deducing method using the coordinate relationship between the reference plane and fringe pattern. The method can make sure the fringe pattern projected to the reference has standard periodicity and can solve the problem of optical distortion in reference plane in traditional phase measurement profilometry produced by divergent illumination. The 3D shape of the tested object can be reconstructed with the help of phase-height mapping algorithm. The proposed method does not need to store the relationship between phase and height as the traditional method. It does not constain the 3D measurement much, simplifies the design of measurement system and has high measuring precision. Computer simulations and experiment results validate the feasibility of this method.