To achieve high precision of linear frequency modulation continuous wave (LFMCW) radar ranging, a kind of LFMCW radar ranging method is presented based on the ImprovedRife (IRife) algorithm. At first, it introduces the principles and implementation steps of this method. And then, it implements this algorithm on FPGA of EP4CE55EF23A7N model. Finally, the algorithm embedded into the LFMCW radar ranging system is performed in field test. The simulation and experiment results verifying the effectiveness of this method show that IRife algorithm reveals its small rootmeansquare error (RMSE) and high ranging precision and stability compared with the Rife algorithm under the condition of the same signaltonoise ratio (SNR).