Abstract: The compression properties of soil aggregates are an important reference index in the process of calculating settlement and deformation of some foundations. In order to understand the compression properties of the sandstone-mudstone mixture treated for different soaking times, 7 different soaking time plans and 2 different saturation ways are set up in this paper. A confining compression test method is adopted to finish the exploration that how the soil aggregate’ intensity changes when the sandstone-mudstone mixture is soaked for different times. The experimental analysis results show that, comparing with the data without immersed specimens, the axial deformation increased by 11.48% after 1 h of the soaking time in the experimental scheme. And the compression modulus decreased by 31.22% and the compression coefficients increased by 45.03% after 5 d of the soaking time. Further, comparing the test results of the soaking time in 1 h, the axial deformation increased by 47.40% and the void ratio decreased by 7.71% after 5 d of the soaking time. Thus, the compression modulus was reduced, the compression coefficients increased, and the deformation increased along with the soaking time prolonged for the soil aggregates. The analysis above suggests that the compression modulus, the compression coefficients and the compression index should be combined to evaluate the sandstone-mudstone compression properties under the conditions of long-term immersion. And it also suggests that the compression coefficients should not be separated from each other to evaluate them. In addition, it is found from analysis of data under different soaking times that the stress-strain curves present a series of straight lines when they are in the lnε-ln p coordinate. These lines show a shape of broom-part and also have a convergence trend in that coordinate. The difference of test data is within 5% between the vacuum way and the immersed way. Thus as a result, the two saturation ways have no significant influences on the compression properties of the sandstone-mudstone mixture.