Based on the selective non-catalytic reduction （SNCR） denitration in the furnace, a two-dimensional two-phase flow model with a symmetrical structure was abstracted from the problem of gas-liquid two-phase flow. Numerical simulation was conducted to discuss the flow and mixing characteristics of gas-liquid two-phase relative impulse flow. The simulation results show that due to the disturbance of high-speed gas flow in the furnace, the liquid jet can't penetrate the gas zone and converge near the center line of the model at all of Reynolds numbers. With the increase of Re, the liquid penetration increases, and the liquid jets with opposite sides can gradually converge in the model. There is a confluence point between the left and right liquid jets when Re is 464 807. When Re continues to increase, the position of the convergence point moves up, and the gas-liquid two-phase fluid mixing in the upper calculation area is more uniform. If Re continues to increase, the position of the convergence point does not change much, and the two-phase mixing efficiency becomes worse because the liquid flow out of the computation zone for its too much momentum. At last, as physical and geometric interference is eliminated in this simulation, the asymmetric gas-liquid two-phase flow in the furnace with symmetrical structure may be caused by the nonlinearity of the problem.