The invention relates to a method for reducing converter slag by utilizing coal gas and recycling furnace slag. The method comprises the following steps: dividing a converter smelting process into a converter steelmaking process and a converter slag thermal treatment process, wherein in the converter steelmaking process, impurity elements in molten iron enter the converter slag in the form of oxides by virtue of oxidization reaction, thereby forming thermal-state converter slag with high phosphor content; pouring the converter slag into a treated slag filling unit, carrying out the converter slag thermal treatment process, transferring the slag filling unit with the converter slag to a converter slag treatment station, enabling the converter slag to generate thermal-state reduction taking the coal gas as a reducing medium in the converter slag treatment station, wherein a reducing proportion of FeO is greater than 80%, and a reducing proportion of P2O5 is greater than 80%; and while carrying out the thermal-state reduction treatment process, recycling waste heat of the converter slag and recycling gaseous-state phosphor, and taking the treated converter slag as pre-melting slag, and returning the pre-melting slag and an iron-containing cooling material into a converter for reapplication.