Abstract: To suppress intrinsic noise and improve signal-to-noise in the interferometric system, a new light source named ring source is described. The reason that the ring source can reduce the intrinsic noise while preserving the fringe contrast of the interferogram is given. Using the fringe contrast and the spatial frequency of the intrinsic noise, the outer and inner radii of the ring source are obtained. Experiments of comparing with traditional point source show that ring source can suppress coherent noise effectively and preserve the fringe contrast. The power spectral density of intrinsic noise is less than one tenth that of point source at spatial frequency less than 2.5 mm-1 and the signal-to-noise ratio is more than twice that of point source at spatial frequency less than 2 mm-1.