To study the suppression effect and mechanism of porous silicon carbide on hydrogen explosion accidents in hydrogen-powered ships, a semi-open combustible gas suppression experimental platform was built. By changing the placement position, pore size, and equivalence ratio of porous silicon carbide, the effect of suppressing hydrogen-air premixed gas explosion was explored, and the explosion suppression mechanism was analyzed by numerical simulation. Results show that the suppression mechanism of porous silicon carbide on hydrogen-air deflagration includes heat absorption and cooling, flame quenching, and overpressure attenuation. However, porous silicon carbide can also disturb the unburned gas, causing deformation of the flame shape, thereby intensifying the deflagration. Under the same pore size and equivalence ratio conditions, the suppression effect is significant when the material is close to the ignition source, because when the flame reaches the surface of porous silicon carbide, the pressure difference on both sides is small, thereby reducing the flow velocity of the flame in the pore, interrupting energy transfer and extinguishing the flame. When the hydrogen-air equivalence ratio is 0.4 and the distance from the ignition source is 110 mm, porous silicon carbide with 40 PPI and 50 PPI can effectively suppress hydrogen flame propagation, and the peak flame velocity is reduced by 5.2 m/s and 12.5 m/s, respectively, and the attenuation rate of overpressure peak is 26.5% and 7.2%, respectively. At a distance of 220 mm from the ignition source, porous silicon carbide with 50 PPI can effectively extinguish most flames, reducing flame speed and peak overpressure by 10.5% and 13.9%, respectively. When the distance increases to 330 mm, the three types of porous silicon carbide pore sizes can not effectively prevent flame propagation. On the contrary, due to their destructive effect on the flame front, the detonation reaction became more intense. Under different equivalence ratios, differences in energy release and reaction rates directly affect the suppression effect of porous silicon carbide, when the equivalence ratio drops to 0.3, the explosion suppression effect of porous silicon carbide is enhanced, and when the equivalence ratio is increased to 0.5, the energy release increases, leading to weakening of the suppression effect of porous silicon carbide.