Abstract: The longitudinal pulse detonation phenomenon (LPD) in the annular combustor is experimentally studied, and the operation process of this mode is analyzed through the combination of the high frequency dynamic pressure measurement and the high speed imaging. The results show that for the hydrogen and air mixtures, the LPD occurs under the condition that the blockage ratio at the exit is larger than or equal to 0.6 and the air mass flux at the minimal cross-sectional area is greater than 200kg/(m²·s). The LPD in the combustor undergoes decoupling and re-initiation in each cycle, and the shock wave reflected from the exit develops into a detonation at the head of the combustor, accompanied by severe luminescence. The average propagation velocity of the detonation wave in each cycle is comparable to the sound speed of the combustion products, which leads to the usage of the linear acoustic theory to predict the operation frequency.