As the sinusoidal signal can be concentrated in the Fourier domain due to the orthonormal sine basis of the Fourier transform. The linear frequency modulation (LFM) signal can be concentrated in the fractional Fourier domain due to its orthonormal chirped basis of the fractional Fourier transform. So the detection and parameter estimation of LFM signal is usually completed by step-based searching method for extremum searching in the fractional Fourier domain. In order to resolve the disadvantage of inefficiency of step-based searching method, Chaos optimization algorithm is introduced to the fractional Fourier transform for extremum searching based on the study for the nature of fractional Fourier optimization problem. Simulation results show that the performance of Chaos optimization algorithm is better than that of the traditional step-based method.