Abstract: The effective influence radiuses of different mechanical properties of coal under hydraulic punching are achieved through theoretical analysis, which can provide theoretical basis for engineering determination of hydraulic punching influence radius. Then, the actual punching influence radius of by pressure method and relative pressure method is got. The research shows that negative pressure method can be used to replace pressure method when the influence radius can not be effectively measured under the bad permeability coefficient and large gas diffuse of the initial velocity seam.