Abstract: In order to analyze the coal wall spalling, dilling bit jammed and other problems occurred in the seam gateway driving in the seam after the hydraulic sIo tting, punching and other hydraulic pressure releasing and permeability improved technology conducted, a physical similarity simulation combined with a particle flow so ftware PFC numerical simulation method was applied to simulate and analyze the internal stress and crack dynamic evolution process of the slotted seam under the sur rounding pressure condition and to discuss the damage and failure features after the seam slotted. The results showed that when several slots made in the seam, a stre ss concentration would be occurred at the end of the adjacent slot and the damage development would occurred in the seam. Thus the pressure released role of the se am at the top and bottom of the slotting profile would be obvious. With the thickness of the slot increased, the pressure released effect of the slot profile would be incre ased, the seam would be damaged and deformed easily and the porosity would be obviously increased. The slotting within the seam would strengthen the uneven of the seam stress field and the crack field, the stress at the slot end and boundary would remarkably increase the unstability of the seam and the designed rational slot size would be an effective method to reduce the drilling difficulty of the seam gateway and the maintenance difficultyt of the gateway.