To suppress methane explosions and reduce accident occurrence, this study employed a self-made vertical explosion pipeline platform to investigate the suppression characteristics of brucite powder on premixed methane-air explosions. The effects of equivalence ratio, suppressant concentration, and powder particle size on methane explosion pressure and flame propagation were systematically analyzed. The main findings are as follows. Under fuel-lean conditions (Φ = 0.8), the suppression effect was most pronounced: the flame color changed from pale blue to dull orange-yellow, the average flame propagation velocity decreased by 41%, and the explosion pressure dropped by about 28.6 %. Under fuel-rich conditions (Φ = 1.2), the flame velocity reached its maximum (30 m/s), yet the corresponding pressure rise was the most gradual, indicating a pressure-velocity decoupling phenomenon. When the powder concentration reached 200 g/ m^{3} , the explosion pressure decreased by 61.1 % compared to the blank group condition; the maximum and average pressure rise rates were reduced by 78.2 % and 81.1 %, respectively; the time for the flame to reach the top pipe outlet extended from 28 ms to 63 ms; the flame velocity dropped from 21.4 m/s to 9.5 m/s. This study also characterized the physical properties of brucite powders with three different mesh sizes. Among the three mesh sizes, the 1250-mesh ultrafine brucite powder exhibited the strongest inhibition performance: the explosion pressure dropped from 0.036 MPa (blank group) to 0.025 MPa, and the flame propagation velocity decreased from 21.4 m/s to 12.5 m/s. This study can provide a scientific basis for developing effective explosion prevention and suppression measures.