Abstract: Most of the wastewater treatment plant (WWTP) process unites consist of multi parallel series. In applications, under the influence of interference factors the discharge distribution of these series are unbalanced, which will bring lots of adverse effects to the WWTP operation. Therefore, a convenient method is needed to accurately assessment the flow distribution. To solve this problem, a method was proposed to assessment WWTP flow distribution based on material balance principle, by monitoring the fluctuations of indicator values between inlet and outlet flow, numerical fitting and dynamic time warping (DTW) algorithm was associated to assessment the flow distribution. This method was applied to a large WWTP. Result shows good fitting of actual values and predictive values, the linear correlation coefficient is 0.948, and the average error is -2.5%. This method has certain reference for the WWTP operation.