Vacuum thermal environment test is an indispensable experimental project in the development of spacecraft. A large number of test cables need to be configured during the experiment, so the fault detection of test cables is of great significance. In order to effectively improve the positioning accuracy of test cable faults, this paper studies the application of wavelet transform and fractional Fourier transform in cable fault test. The transmit signals of the TDR and FDR cable fault detection methods are subjected to noise addition processing, and the corresponding time-frequency analysis methods are respectively used for denoising. The simulation results show that the wavelet transform and the fractional Fourier transform have good denoising effect, which is of great significance to improve the fault location accuracy of the test cable.