Abstract: Transient phenomena often happen in water distribution systems (WDS). In order to accelerate system transformation from unsteady state to steady state, two mathematical models were proposed based on the theory of transient flow, which are the method of characteristics (MOC) with re-divide damping coefficient and the lattice Boltzmann equation (LBE). These methods were used to calculate an example in WDS. It is shown that LBE is more accurate when Reynolds number is less than 7 000, otherwise MOC is more precise.