A river course ecological treatment system essentially comprises a plurality of ecological biological water purification systems and a plurality of plastic retaining dams disposed along a river course, and at least one damp land ecological water purification system disposed beside the river course. The plastic retaining dams separate the river course into several retaining regions. The ecological biological water purification systems purify the water in the retaining regions by microorganism purification. Afterward, the water purified by the ecological biological water purification systems is introduced into rainwater channels of the at least one damp land ecological water purification system. After being purified by aquatic plants in the at least one damp land ecological water purification system, the water returns to the retaining regions the downstream portion of the river course. Therefore, a river improvement system capable of performing both step-by-step treatment and joint treatment is effectuated.
