An important phenomenon in gaseous detonations is the formation of high velocity jets of products and their influence on the detonation front. In this paper، an adaptive second-order Godunov scheme along with a front tracking algorithm is used to carry out two-dimensional numerical simulation of gaseous detonation in a channel. For the chemical kinetic, a single-step Arrhenius rate law is utilized. The initiation of detonation is performed using a plane blast wave. The structure of the front (that includes triple points ,transverse waves ,incident shock ,and mach stem) is fully formed as the detonation propagates in the channel. The results show that the origin of high velocity jet from product is the interaction of two transverse waves and their corresponding triple points ,or the impact of one triple point to the wall boundary. The influence of the high velocity jets on the detonation front and the increase of mixing between unburned and burned gases is investigated.