Due to the stray light and electromagnetic interference in the environment, as well as the differences in the length and reflection characteristics of different paths, the FMCW liDAR system will be affected by multipath interference when receiving the target echo signal, and there is noise interference, which makes the accuracy of target ranging is low. Therefore, the FMCW LiDAR ranging method under the influence of coarse spatial resolution is proposed. According to the transmitting signal and echo signal of FMCWN laser radar system, IF signal is obtained. The EMD algorithm is used to decompose the IF signal, calculate the mutual relations between the IMF components of the signal, and determine and eliminate the IMF components with noise. The SFFT algorithm is used to refine the frequency spectrum of the IF signal after noise removal, obtain its estimate, determine the correction direction, correct the frequency estimate, and determine the distance of the measured target by using the corrected frequency of the IF signal. The experimental results show that the proposed method has good denoising effect, high spectrum estimation accuracy, high ranging accuracy and high ranging efficiency. The root mean square error of ranging is less than 0.04, and the longest time is only 0.23 ms.