<p>The method of automatically formed roadway by roof-cutting and pressure-relief without coal pillars (AFRRPCP) represents an innovative approach in longwall mining. Its core technology lies in directional roof-cutting. However, the conventional explosive energy-concentrated blasting used for roof-cutting presents significant safety risks and difficulties in precisely controlling blast-induced damage. To address these challenges, this study proposes a novel non-explosive roof-cutting method—instantaneous expansion single fracture (IESF)—and systematically investigates its pressure relief effects. Through theoretical analysis, the structural characteristics of IESF and its directional rock breaking mechanism are revealed. A damage model considering rock heterogeneity is developed using the finite element method, elucidating the crack propagation law driven by quasi-static gas expansion. Numerical results indicate that the synergistic regulation of hole spacing and charge amount facilitates stress superposition between adjacent holes, leading to the formation of a low-disturbance continuous fracture surface. Field engineering tests demonstrate that IESF achieves high-precision two-dimensional directional fracturing with minimal vibration impact and negligible surrounding rock damage. Monitoring data validate that IESF effectively interrupts the stress transmission path between the roadway and the gob roof, significantly reducing the roof pressure. The average working resistance of hydraulic supports is reduced by up to 31.6%, demonstrating a notable pressure relief effect. Simultaneously, roadway deformation is effectively controlled, with a 39.1% reduction in roof-to-floor convergence, greatly enhancing roadway stability. The findings of this study not only expand the application scenarios of IESF technology but also provide a safer, more efficient, and controllable non-explosive roof-cutting method for AFRRPCP, promoting the advancement of green and efficient mining technologies.</p>