Most mature reservoirs in China are facing severe conformance problems causing excessive water production, high water cuts, and low recovery factors due to the severe heterogeneity. Among these conformance problems, high-conductivity channels, such as large fractures and void space conduits, could cause fast communication between injection and production wells, limiting the sweep efficiency. Therefore, plugging high-conductivity channels plays a crucial role in water/gas flooding and the enhanced oil recovery process. This work systematically elucidates several commonly used plugging agents, including their basic compositions and properties. We summarized the field pilot results and came up with the current problems and several suggestions for the further development direction of plugging agents. Hopefully, this work could provide valuable guidance for plugging high-conductivity channels in mature reservoirs.