Abstract: With the implementation of the medium and small-sized river harnessing projects, it is necessary to reform hydrometry methodology and explore technological innovation for flow measurement. Thus, two optimization experiments for velocity measuring vertical lines were implemented by hydrometeorology undergraduates of Nanjing University of Information Science and Technology in this study. The measuring velocity data of multi-vertical lines of the two experiments in Yuliang hydrologic station were collected. Since the original reduction algorithm was likely to omit the most representative vertical line in the process of searching for the optimal flow error, a new algorithm was designed to directly search the vertical lines of the minimal flow error. Then the impacts of the two algorithms on flow errors were analyzed. The results showed that: the 13 vertical lines selected by the constant velocity measuring method were proved to be well representative. They could be used to calculate discharge with high accuracy in current survey. The new algorithm uses the same number of vertical lines, but with smaller flow errors. According to the results of the new algorithm, the single vertical line located at 84m apart from the starting point may be considered as a simple scheme for single vertical line flow measurement in the case of specific hydrologic circumstance. The flow relative error presented an obvious exponential decreasing tendency as the increase of the selected vertical lines. The reduction algorithm of this research is beneficial to enhancing the experiment accuracy. The results offer reference for the daily work of vertical lines reduction and the reformation of flow measuring method for the basic hydrologic stations.