By using grating imaging effect, a grating imaging reflection interferometer can be formen. Combining Moire method, reflection moire fringes which represent partial slope contours of out-of plane displacement of a mirrored surface specimen will be gotten on the self imaging plane of the interferometer.Comparing with conventional reflection moire method, this new method is a real time one and it no longer needs a high quality camera refqired by the conventional method. Both theoretical analyses and experimental vesuls are presented.