As a vital energy source, methane poses significant explosion risks that threaten industrial safety. To address the limitations of conventional methane explosion suppressants, a modified dry water gel (NH₄H₂PO₄-SCDW) was prepared by incorporating 5 wt% NH₄H₂PO₄, 0.1 wt% sodium alginate (SA), and 0.05 wt% calcium lactate (CL). The physical properties and explosion suppression performance of the composite were systematically evaluated. Experimental results showed that NH₄H₂PO₄-SCDW exhibited not only excellent structural stability and water retention capability, but also rapid water release under high-temperature conditions, thereby effectively suppressing explosions. In pipeline explosion tests, NH₄H₂PO₄-SCDW exhibited significantly better suppression performance than conventional dry water (DW), with the peak overpressure at pressure sensor 1# reduced by approximately 16.95% on average, and the flame propagation distance shortened by 24.13% at a spray dosage of 0.48 g. Mechanism analysis revealed that NH₄H₂PO₄-SCDW suppresses methane combustion through the synergistic effects of physical and chemical inhibition, effectively interrupting the combustion chain reaction. This study provides theoretical support and experimental evidence for the development of high-efficiency and environmentally friendly fire and explosion suppressants.