Abstract: The existing LFM signal parameter estimation algorithm is hard to fulfill tasks in a real-time system for heavy computation loads.A fast efficient algorithm based on spectrum zoom analysis is proposed.First,the spectrum of the array multiplication of the IF sample and its delayed version is analyzed to obtain the rough estimate of the chirp rate,then chirp-Z transform is applied to estimate the chirp rate accurately.Second,using the direct de-chirp method with the estimated chirp rate,the estimation of the initial frequency of the LFM signal can be done.The spectrum zoom method can also be used to improve its accuracy.Simulation results show the proposed algorithm is effective.