Abstract: Compression deformation tests of bulky rock material that in saturation conditions and natural conditions were carried out.In order to provide the reliable theory basis for engineering practices,the compression deformation mechanism and rules of bulky rock material was discussed,the results showed that:1) compression characteristics of bulky rock material is performance of the low compressibility,the compression deformation is given priority to plastic deformation and also performance of the instantaneous deformation; 2) compression modulus in saturation conditions is obviously less than the one in natural conditions,so bulky rock material produce large deformation in saturation condition;3) the pressure characteristic value of compression deformation is 400kPa,when the pressure is greater than this value the compression modulus is lower,and the deformation is increase,void ratio is also reduced obviously; 4) the rock softening action intensifies bulky rock material compression deformation.