In order to improve the accuracy， a new method is proposed to obtain the corneal topography based on phase measurement deflectometry and the traditional placido disk system. The proposed method utilizes a geometry configuration where the normal at the apex of the human eye is collinear with the optical axis of the camera and parallel with the normal of the screen.Two-dimensional orthogonal fringe pattern displayed on the screen is reflected off the human eye， and the deformed fringe image is recorded by camera. Then the coordinates of the screen and human cornea are calculated by phase extraction algorithm and iterative algorithm， respectively. According to the geometric relationship between them， the corneal topography can be obtained. The numerical simulation demonstrates that the measurement accuracy of the radius of curvature and diopter of the model eye can theoretically reach ±14.7 μm and ±0.07D， respectively. Finally， experiments are conducted to measure a spherical element with a radius of curvature close to that of the human eye. The results show that this method has the advantages of highaccuracy， simple deviceand low cost.