Abstract: The fracturing radius, as a key indicator characterizing the energy transfer of mine blasting and the fragmentation effect of rock mass, its precise determination is directly related to the safety and energy efficiency of blasting engineering. However, due to the heterogeneity of complex geological structures, the irreversibility of the dynamic crack evolution mechanism and the limitations of in-situ monitoring technology, there are still significant technical bottlenecks in the in-situ detection of the fracturing radius at present. Aiming at this engineering problem, based on the unique chemical inertness, strong diffusion characteristics and highly sensitive detection advantages of sulfur hexafluoride (SF₆) gas, an in-situ dynamic detection method based on the tracer principle of SF6 gas is proposed, and a multi-module coupled crack radius detection system is developed. Combined with the migration law of gas diffusion concentration in three-dimensional space, the quantitative relationship between the SF₆ diffusion field and fracture development is identified. This system integrates the gas supply unit (SF₆ storage tank and pressure stabilizing control), the adaptive sealing component (with a pressure resistance of 2.5 MPa), and the distributed gas detection array (detection accuracy of ±0.1×10⁻⁶), and forms a closed tracer gas circulation monitoring system through airtight pipelines, burst holes, and observation holes. In-situ blasting cracking tests were carried out at the 10102 top extraction roadway excavation face of Yuwang Coal Mine. The spatial concentration gradient analysis method was adopted to establish a quantitative evaluation model of SF₆ diffusion field and cracking radius. The results show that: when the volume fraction threshold of SF₆ was set at 150×10⁻⁶, the effective fracturing radius of the blast hole reached 1.0 m (confidence interval ± 0.15 m), and its asymmetric distribution characteristics were significantly correlated with the geological structure. Engineering verification shows that after optimizing the blasting parameters based on this detection result, a 17% reduction in the charge per hole can still meet the fracture propagation requirements, verifying the engineering applicability of the system.