Fiber length measurement technology plays a crucial role in the field of light sensing, and how to accurately measure fiber length is a research hotspot in this field. The laser frequency modulation interferometry technique has the advantage of high spatial resolution measurement, which can be used in the field of fiber length measurement, but the frequency modulation nonlinearity will lead to spectral broadening, which affects the ranging accuracy. This paper proposes a fiber length measurement technique based on the Lomb-Scargle method, which can obtain more accurate measurement values while correcting the nonlinearity, and its measurement range is not limited by the optical range difference of the auxiliary path. As a verification, about 1.2 m long fiber length measurement experiments, the absolute error of the measurement of this method is basically stable within 50 μm, with a high measurement accuracy. This method provides a way of thinking for the nonlinear correction of laser frequency modulation interferometry.