The invention discloses a method for measuring a slag amount of a converter. The method comprises the following steps: firstly pre-embedding cerium oxide serving as a tracer agent into the bottom of steel ladle; during steel tapping of the converter, adding a slag former; then blowing argon at an argon station to enable ladle slag to be uniform; putting molten steel into an LF (Ladle Furnace) for heating; taking multiple slag samples from different positions of the LF, thus obtaining the percentage of the cerium oxide serving as the tracer agent; and obtaining the slag amount of the converter according to the adding amount of the cerium oxide serving as the tracer agent, the adding amount of the slag former and the percentage of the cerium oxide serving as the tracer agent. The method can accurately measure the slag amount of the converter.