Detonation initiation and propagation of premixed gas in the confined channel are greatly influenced by external factors, such as initial pressure, channel size, etc. Using the self-made narrow gap with different heights, influences of different initial pressures and heights on detonation initiation characteristic and propagation process of C₂H₄/O₂ combustible premixed gas were investigated. The results show that different initial pressures and gap heights does have great influence on detonation initiation, especially the continuous decrease of gap height may shows different DDT characteristics of the conventional channel. In addition, velocity deficit of detonation wave is bound up with initial pressure and gap height at the same time, and the deficit value is proportional to . Considering the limitations of the experimental results, in order to obtain more accurate experimental data, they need to be repeated in the following experiment.