Low weir is widely applied to the sluices and low dams in plains. Its discharge capacity directly determines the layout of discharge buildings of low head water control project and the engineering benefit. However, in practical projects, the discharge capacity of low weir is influenced by many factors. Based on the processing and analysis of various data, and in consideration of different weir shapes, weir heights and weir surface slopes at upstream and downstream, etc., this article analyzed and studied the relationship between discharge capacity and the shape of low weir, and by taking project cases, it put forward relevant problems in engineering application which should be noticed about the design and type selection of low weir in different conditions.