Abstract: In order to solve the problem of finding the limits of subsurface blasting in gas drilling, a device for quickly and directly measuring the blasting limit of formation hydrocarbon gas at wellsite was developed. A test method corresponding to this device was proposed and the rapid measurement test was carried out. The test results suggested that this test method could accurately measure the blasting limit of formation hydrocarbon gas under different pressures, temperatures and mixed gas volume fractions, and obtained the blasting range of current formation hydrocarbon gas. Thus this method could prevent the occurrence of subsurface blasting. In the case of methane gas, the measurement result for methane gas at 0.1 MPa verified the effectiveness of the device and revealed the influence of temperature and pressure on the blasting. The research indicated that the successful development of gas drilling subsurface blasting limit measurement device and the proposal of corresponding measurement methods provided an effective preventive measure for addressing the subsurface blasting problem in gas drilling. Thus this device showed the potential for wide application and adoption.