Abstract: In order to evaluate the control of rocks in roof and floor coal seam on coal seam hydraulic fracturing fractures, cores of coal and coal seam roof have been served in rock mechanical parameter test to get rock mechanical parameters, including compressive strength of coal and rock, tensile strength, elastic Modulus and Poisson's ratio. The tested core depth is returned to the sonic log depth. After the sonic log response is standardized, the core longitudinal sonic time difference is calibrated. The relationship between the mechanical parameters of coal and rock and the time difference of longitudinal waves is fitted. Moreover, prediction model of rock mechanical parameters based on the response of sonic logging is constructed which is used to calculate the mechanical parameters and ratios of coal and rock. The differences in rock mechanical properties between coal seam and roof and floor are evaluated. These results show that the elastic modulus of the roof rock in the study area is generally more than 6 times larger than that of the coal seam, and the compressive strength is more than 5 times larger than that of the general coal seam. Therefore, coal seam fracturing fractures are easily controlled in the roof but not in the floor. In the southeastern part of the study area, hydraulic fracturing fractures can easily reach the roof and floor.