The RKDG（RungeKutta discontinuous galerkin）method that is the combination of discontinuous galekin method for space discretization together with an explicit RungeKutta approach for time derivatives has been adopted to show the 3D simulation of a Z type ultrasonic flowmeter in water flow measurement field, which divided into flow field and sound field. Based on the stationary background meanflow obtained by solving the standard k－ε model, the control equations are derived from continuity, momentum, and equation of state to describe the propagation of linear acoustic wave in an adiabatic way. The acoustic characteristic is shown in figure when it moves in the direction of the main flow with the presence of a background flow by defining the normal velocity on the surface of transmitter. Through the recalculation, the average sound pressure on corresponding surface of receiver under upstream propagation can be generated by simply switching the source and receiver boundary, as the difference in travel times by comparing the average sound pressure for downstream and upstream propagation which is lower than experimental result. This numerical methodology opens the possibilities in simulating acoustic propagation in other complex configurations, as well as complicated flows.