Methane explosion is one of the major hazards in the mechanical industry. In this paper, a series of methane/air premixed combustion experiments were carried out to study the influence of blockage ratio on flame propagation. The blocking ratio (BR) is referred as the cross-sectional area of occlusion divided by the total area. Flame shape and pressure response were measured and analyzed. The results showed that five typical stages were experienced for all configurations except for BR = 0.999, particularly, a diamond-shaped flame and a mushroom-shaped flame front were observed for some lower BRs. The largest length of jet flames was selected to characterize flame–obstacle interaction rose smoothly until BR = 0.9 and then declines rapidly. The flame evolution process was simulated by a power-law flame wrinkling model. Flame behaviors and pressure dynamics for each configuration were investigated, and the maximum flame speed, explosion pressure, and growth rate coincide exactly with the largest length of jet flames in trend. It can be seen that BR was of great significance to flame propagation and BR = 0.9 was a limit or a watershed. In addition, the pressure growth rate was positively correlated with the flame tip speed.