Experiments on the suppression effect of ultrafine MAP powder in methane/air explosions were conducted in a 120 L combustion chamber with a methane concentration of 10%. The use of ultrafine MAP powder was described with various triggering times and amounts of powder that could influence their effectiveness. The results showed that by increasing the amount of ultrafine MAP powder, the performance varied from promotion to suppression. The suppression action of the powder inhibitor was superior to the disturbance action, as reflected by the curve of explosion pressure and cross-sectional area normalization. By decreasing the triggering time, excellent suppression performance was presented and showed that suppression approached prevention. According to the experimental result, a few powder suppressant and nitrogen could not behave collaborative explosion suppression.