Abstract: In random lasers, fiber Bragg gratings (FBGs) and cascaded multi-FBG configurations are extensively employed as wavelength-selective components. However, the modulation depth of FBGs exerts a non-negligible influence on the output performance of random lasers. In this study, two cascaded FBGs were taken as the research subject, and the effect of discrepancies in FBG modulation depth on the output spectrum of random lasers based on Rayleigh scattering feedback was comparatively analyzed. When the modulation depths of the two FBGs were 3 dB and 6.3 dB, respectively, only the FBG with a modulation depth of 6.3 dB enabled random lasing at its central wavelength due to gain competition. When the modulation depths were 5.5 dB and 6.3 dB, respectively, stable dual-wavelength random lasing was achieved; within a 1-hour period, the wavelength drifts were 0.060 nm and 0.044 nm, while the peak intensity fluctuations were 1.439 dB and 1.486 dB, respectively. The findings of this research can provide valuable insights for the design of wavelength-selective components in random lasers and the investigation of random laser performance.