A fringe position measurement method is proposed based on the spatial optical path difference modulation, which is applicable to fringe searching and fringe tracking. When combining the two beams from the two ends of a baseline, a static optical path difference modulation is brought in by a beam combiner introducing tilt angle. An imaging lens is used to image the interferogram onto a CCD detector. The translation of the white-light fringe packet is related to the optical path difference between the two combined beams. The position of interference fringe can be computed with the acquired fringe and used to calculate the path difference. The evaluated optical path difference value is further used to cancel the path difference error by the delay line and to stabilize the fringe. The numerical simulation and experimental results indicate that the maximum experimental measurement error is 0.159 μm, which is smaller than the average wavelength 0.555 μm of the broadband light used in the research, the proposed method can achieve the accuracy that meets the requirement of fringe coherencing . Compared with the previous temporal optical path difference modulation method, the proposed method is simple in principle and algorithm implementation, moreover insensitive to atmospheric turbulence.