Abstract: Modulation signal bispectrum (MSB) aims to analyze the fault characteristics in the signal from the perspective of modulation spectrum and carrier spectrum, but the low amplitude of the bogie gearbox bearing faults at the initial stage brings great interference to the demodulation process. In order to solve this problem, this paper proposes a new optimized modulation signal bispectrum (OMSB). Through the reconfiguration of the amplitude in the frequency domain, the proportion of different feature information in the signal can be effectively adjusted, which in turn enhances the amplitude of fault features in the bispectrum domain. By demodulating the signal based on the primary coupling relationship between the frequencies of conventional bispectral signals, the feature information in the signal can be resolved. Meanwhile, the bispectrum signal-to-noise ratio is proposed for quantitatively evaluating the fault features in 2D data, optimizing the bispectral demodulation results and clarifying the features. The effectiveness of this method in the diagnosis of bogie gearbox bearing faults is verified by simulation and experimental signals.