An improved nonlinearity correction algorithm by hardware-based equispaced-phase resampling for frequency modulated continuous wave (FMCW) ranging system was proposed. After improvement, equispaced-phase resampling method could be realized in one step by hardware data acquisition. No subsequent complex data processing is needed any more, which will save much memory space and data processing time. Moreover, compared with software-based equispaced-phase resampling method, the improved method had higher sampling accuracy. The effect of nonlinear frequency modulation on ranging precision of FMCW ranging system and the principle of equispaced-phase resampling for nonlinearity correction were explored. On this basis, a new spectral analysis method was presented for the reason that the equispaced-phase resampled data was not equally spaced in time domain and the traditional spectral analysis method is no longer applicable. The computational formulas of peak spectral frequency and object distance were deduced. Their correctness was verified by simulation. Experimental results show that equispaced-phase resampling based on hardware has higher ranging precision and resolution than equispaced-phase resampling based on software, and the former is simpler.