Abstract: In order to investigate the effect of different slot parameters on coal damage and crack propagation under water jet technology,the single slot and double slot coal sample parameters model were established by PFC2D software. The damage process of sample under the condition of 90°,45° and 0° angle under the uniaxial load were simulated,and the total stress-strains were compared and analyzed. The distribution of cracks,the number of cracks and the internal friction energy in coal were also discussed. The simulation results show that the fast development of coal crack in the plastic deformation stage were that the internal friction can increase with the increase of the internal friction,and the cracks were distributed at both ends of the cutting slot. The layout of the multi slot would guide the development of the crack orientation,and the increase of the number of slot surface and the angle between the increase slot size and the load stress could reduce the threshold of the coal crack development. The design of water jet slotting process layout should choose the angle between the slot surface and the main stress as 45°,and avoid the wrong angle of 0° between the slots.