A parameter-estimation method based on subsampling for multi-component linear frequency modulated (LFM) signal is proposed. The received signal is subsampled by multiple analog to digital converters (ADCs) with identical sampling rate and different sampling time. The total sampling rate of all ADCs is lower than the Nyquist rate of original LFM signal. As the product ambiguity function of a single subsampling sequence is a single tone, the chirp rate is estimated by searching for the peak of the product ambiguity function. Then dechirp operation is conducted for all subsampling sequences to obtain multitone signals, from which the initial frequencies of LFM components are estimated by solving moment-preserving problem and over-determined equations. In the proposed method, parameters of the LFM signal are estimated from sub-Nyquist samples, and the estimation is easily realized with simple operations. Simulation results verify the effectiveness and accuracy of the proposed method.