The invention provides a method for measuring martensite content in heat rolling dual-phase steel. The method comprises the following steps in sequence: forming a sample to be measured of the heat rolling dual-phase steel with a smooth surface; performing grinding and burnishing on the sample to be measured, and placing the sample to be measured into a mixed solution for corrosion, wherein the mixed solution is prepared by mixing a water solution of sodium metabisulfite with the mass concentration of 0.85-1.4% and a alcoholic solution of trinitrophenol with the mass concentration of 3.9-4.2% according to the volume ratio of (0.9-1.1):1; cleaning and drying the sample to be measured; shooting a plurality of electronic photos in the thickness direction of the sample to be measured; using metallography image analysis software to process the plurality of electronic photos to obtain the martensite content of the sample to be measured. The invention has the advantages that the method can realize complete statistics for a differential view field, can increase contrast degree of grayness of each tissue, and can accurately measure the martensite content in the heat rolling dual-phase steel.