To explore the wetting deformation laws of carbonaceous mudstone cutting slopes, the parameters of Duncan-Chang EB model were determine by carrying out triaxial compression tests. The wetting deformation of carbonaceous mudstone cutting slopes with different slope heights and slope ratios were simulated by FLAC3D. The simulation results indicate that the maximum horizontal displacement and vertical displacement of 16 m secondary carbonaceous mudstone cutting slope with a slope ratio of 1:1.5 per level in dry and wet occurred on the top of the firstly slope and the secondary slope, respectively. Both the maximum horizontal and vertical displacement after humidification increased. When the slope ratio remains constant, the horizontal and vertical wetting deformation of the slope increase with the increase of the slope height. The vertical wetting deformation is about 5～10 times of the horizontal wetting deformation. At the same slope height, the change of the horizontal and vertical slope wetting deformation is not obvious with the increase of the slope ratio.