The invention discloses a coal mine impact ground pressure and harmful gas comprehensive prevention and treatment system and method. Firstly, according to roof lithology and pressure characteristics of a coal mining work face, a target rock layer of horizontal well staged fracturing is determined, according to the target rock stratum and coal seam work face characteristics, a well spacing manner of a horizontal well is determined, the horizontal well is drilled, in the horizontal well, a target rock stratum and a coal seam are subjected to fracturing, through fracturing, the target rock stratum and the coal seam form an inter-communication net-shaped fracture, a ground pump drainage system is built, harmful gas in the coal seam is subjected to pump drainage, the horizontal well is mountedin the target rock stratum, in the horizontal well, the target rock stratum and the coal seam are subjected to fracturing, the inter-communication net-shaped fracture is formed in the target rock stratum and the coal seam, fracturing pressure relief of the target rock stratum is achieved, the stress state of a coal seam roof is changed, happening of an impact ground pressure accident is avoided, and meanwhile, release and pump drainage of harmful gas in the coal seam can be achieved.