Abstract: The structural plane extensively occurs in coal measures, and is one of the key factors affecting the hydraulic fracturing effect of coal/rock. The fabrication time and filling material types of the structural plane were adjusted to obtain the coal/rock specimens without the filling structural plane, or the coal/rock specimens with the filling structural plane. The physical experiment for hydraulic fracturing was carried out to find out the effect and action mechanism of the structural plane type and injected flow rate on hydraulic fracture extension. As indicated by the result, in the condition of the injected flow rate of 50 mL/min, the fracturing pressure of the pure specimens was higher than that of the structural plane specimen, the interval time of the structural plane without filling had weak effect on the specimen fracturing pressure, and the maximum reduction of the specimen fracturing pressure after the adjustment of the structural plane filling materials was 28.79%; with the increase of the injected flow rate, both the fracturing pressure and acoustic emission ring count peak of the specimens with the filling materials of mica and cement were increased; the time duration of the pressure rise stage was significantly shortened; the hydraulic fracture extension at the structural plane gradually transformed from the mode of extending along the structural plane to the mode of extending along the direction of the maximum main stress. The effects of the structural plane type and the injected flow rate on the hydraulic fracture extension mode at the structural plane were caused mainly by the change of the stress condition on the structural plane when the hydraulic fracture extended to the structural plane. The cross extension mode of the hydraulic fracture and the structural plane can be predicted through theoretical analysis. The extension direction of the hydraulic fracture can be adjusted by adjusting the injected flow rate based on the stress condition on the structural plane.