This paper reports a method to improve a degraded range resolution for FMCW radar. The proposed post-processing method can achieve an improved range resolution without increasing a signal bandwidth by eliminating factors that can degrade the range resolution based on the non-negative least-squares method. For an FMCW radar adopting the postprocessing method with the center frequency of 76.5 GHz and the signal bandwidth of 200MHz, simulation results show that the degraded range resolution of 160 cm is improved to 70 cm, and measurements show that two corner reflectors with the radar cross section of 10dBsm located at 70cm range intervals can be distinguished.