Deformation of ductile cuttings from sandstone in the mechanical compaction process was designed through the“experimental system of triaxial rock deformation” ，and the influence on porosity was studied by looking into the deformation characteristics of ductile cuttings． The design indexes are as follows: simulated depth 0 －4 000 m，interval depth 500 m，and pressure range 0 －120 MPa at interval of 1． 5 MPa． The experi- mental results show that the porosity decreases as buried depth increases，indicating a negative relationship be- tween them． The amount of compression was mainly obtained by porosity reduction and cutting deformation． De- formation of ductile cuttings is mainly ductile deformation; and deformation of crystal fragments is mainly ex- pressed as brittle fracture， resulting in decrease of particle size． The research is of certain value for the explora- tion and development of oil and gas．