FM continuous terahertz wave system is limited by the excitation device, resulting in a generally narrow bandwidth, in the detection of samples due to the limited amount of data at a single point, there is not easy to extract the feature signal, to address this problem, this paper proposes a chirp-z transform algorithm based on the Kaiser window. First of all, the original signal is processed by adding windows, and the linear frequency modulated z-transform is used to extract the feature signals of the depth defects in different samples, and different signal processing methods are introduced for comparative analysis, and the results show that the method proposed in this paper reduces the computational complexity while retaining the feature information of the samples in the limited amount of data, comparing with different kinds of composite material detection data processing, which proves the validity and universality of the method.