The application of carbonaceous shale for subgrade filling not only alleviates the shortage of subgrade filler in carbonaceous shale distribution areas but also meets the strategic requirements of “resource conservation and saving ” and “green development ” for infrastructure construction in China.However，such rocks are weak and susceptible to weathering and disintegration，and they exhibit significant strength deterioration when exposed to water.To fully apply them，their performance must be comprehensively understood.In this paper，the basic properties of the carbonaceous shale were studied，and filler gradation was designed.The tests on compaction characteristics of the filler and particle crushing characteristics after compaction，RCBR （California bearing ratio ） variation characteristics under dry and wet cycle conditions，compression properties of the filler and particle crushing characteristics after compression under dry and wet conditions，as well as the rebound modulus of subgrade during water immersion were conducted.The results show that with an increasing degree of weathering，the original shale tends to become clayey，and the microstructure becomes loose.In the compaction process，coarser filler particles mean that they are more difficult to adjust their position to achieve a stable dense state，and particle crushing is more significant.The filler shows strong softening and disintegration properties when exposed to water.The initial RCBR of the filler is 54%，which exhibits a fast-to-slow decreasing trend under dry and wet cycles and finally stabilizes at about 26%.In the compression tests，additional deformation of the filler by wetting after water immersion is extremely significant，and the crushing particles increase greatly.Particle groups that do not crush at optimum water content also crush after saturation.The rebound modulus of the subgrade without water immersion is 140.4 MPa and declines to 82.1 MPa after 6 h of water immersion，after which the decay of the rebound modulus with increasing immersion time is not significant.For practical application，it is recommended to optimize the gradation of the filler，control the maximum particle size，and adopt subgrade structures that can effectively prevent water and control moisture.In addition，it is necessary to avoid using carbonaceous shale filler in positions with developed surface and ground water.