Abstract: Water measuring devices easy to apply widely should have some particular strengths such as satisfactory accuracy, easy observation, and low cost. Towards this goal, a simple direct-reading water measuring device suit to irrigation canals was developed. It is composed of one or two baffles, an ordinary water meter and a water meter well. It is concluded that the ratio of canal discharge to water meter discharge is a constant in both states of free flow and drowned flow. Laboratory experimental results obtained in U-shaped canal also showed that the ratio M approximates to a constant in the two flow states, and the maximum relative errors were 3.60% and 0.45%, respectively. Since 2008, the direct-reading water measuring devices have been installed and operated satisfactorily in Yanyun Irrigation District and Zhuluoba Irrigation District, Jiangsu Province. This device has some characteristics such as simple structure, low cost, convenient measurement, and satisfactory accuracy. It can be used for small irrigation canals.