Flow measurement for agricultural irrigation management or the allocation of water resources is to control accurate and reliable water use. The methods of obtaining the flow include theoretical calculation, setting of water measuring structures, field flow velocity and cross-section factor observations to indirectly estimate the flow. To achieve the purpose of real-time monitoring, stage-discharge rating curve method needs to concert with monitoring and transmission equipment to achieve the purpose. The above methods have their theoretical basis and applicable conditions. This study tries to discuss the flow measurement of large-scale irrigation drainage channel and river, also introduces the characteristics of different flowmeter and application range and flow measurement of the choice of section cutting method analysis. Finally, with four types of flow measurement methods (1. Errors in large scale water structures, 2. Installing new hydrology station for quick measurement method, 3. River multi-path flow conditions, 4. Tidal River), can understand the possible challenges and solutions, then provide water conservancy engineering and agricultural irrigation fields as references for flow estimation.