The principle and the structure of oil shock absorber determine the inevitable occurrence of abnormal sound of cavitation. Through establishing the mechanical model and simulation, this paper analyzes the cause of abnormal sound of cavitation, uses shock absorber abnormal sound detection device to test shock absorber piston rod acceleration signal, compares the test result with simulation, and verifies the correctness of the analysis. Diagnosis about the abnormal sound absorber of the cavitation can be carried out through the analysis of shock absorber piston rod acceleration power spectrum and bispectrum. The results show that the energy of the shock absorber piston rod acceleration power spectrum and bispectrum is obviously different from those of the normal shock absorber after the cavitation occurs, and the abnormal sound can be reduced by replacing oil.