From the basic concept that an interferogram is a contour map in intensity, we present a new simpler method, for measuring the shifts of interference fringes. In this method, as long as a intensity profile is taken on any straight line parallel to the equidistant parallel fringes in the interferogram (or in the interferogram film), the shift of the interference fringe at all points to this straight line can be found and the variance of the physical quantity of interest is calculated thereafter. It allows the meastLring equipments and the automatic analysis to be simplified, and data can be taken at any pomt in tlie interferogram disregarding the position of fringes. Our experiments show that the repeatability error is less than 1.5%. Satisfactory results have been obtained when this method is applied to the measurement of refractive-index profiles of optical fibers with the nondestractive traverse interferometry. As compared with the results from reflection method, the error of the maximum relative refractive-index difference is about 1% and the whole profile curves accord well with eath other.