The invention discloses a method for measuring boiler dry flue gas volume based on coal caloric values and exhaust fume oxygen amount. The exhaust fume oxygen amount can be acquired from the database of a power plant decentralized control system DCS, the coal caloric values are obtained from a power plant coal industrial analysis report, an excess air coefficient is obtained through the calculation based on the exhaust fume oxygen amount, and the CO2 theoretical maximum value is obtained through the calculation based on the coal caloric values. The content of CO2 in the dry flue gas is obtained through the calculation based on the excess air coefficient and the CO2 theoretical maximum value, and the volume and the mass of the dry flue gas are respectively obtained through the calculation based on the content of CO2 in the dry flue gas and the coal caloric values. The measuring method can effectively prevent the strict requirement that the coal component element analysis needs to be calculated based on national standard, simplifies the calculating model of the dry flue gas, and can meet the needs for the online calculation of the dry flue gas of a boiler.