In the signal processing of radar altimeter close-range altimetry, the frequency spectrum obtained by Fast Fourier transform has the problem of insufficient frequency resolution, which needs to be further analyzed in detail. Chirp_z Transform (CZT) algorithm is an important method in signal spectrum refinement analysis, but because of its complicated algorithm, it is difficult to realize in engineering. Starting from the principle of Chirp_z algorithm, based on DSP Builder and Simulink platform, this paper builds the operation model of Chirp_z algorithm. The model operation results can meet the needs of engineering applications by comparing the accuracy of the model with the Matlab operation. The built model generates a complete hardware engineering file, and has passed the RTL (Register Transfer Level) level simulation verification in the Modelsim software. The model can be completely transplanted into the FPGA and run successfully. The implementation of this algorithm is accomplished through modularization. Compared with the traditional DSP implementation, its system has the advantages of fast calculation speed, stability and reliability.