The invention discloses an engine fuel consumption rate calculation method based on a mole number balance principle, and belongs to the technical field of engine fuel consumption rate detection. The method is characterized by comprising the following steps: step 1, calculating the mass fractions of various fuels; 2, solving the total air inlet molar flow; Step 3, obtaining the volume fraction of each gas, the smoke intensity of the soot and the fresh air inlet flow; 4, establishing a combustion reaction model; 5, obtaining the fuel consumption rate of the engine under the condition that the engine does not contain a carbon smoke part; Step 6, obtaining a fuel consumption rate corresponding to the soot part; And 7, obtaining the actual fuel consumption rate of the engine. In the calculationprocess through the engine fuel consumption rate calculation method based on the mole number balance principle, all important gas components and soot are considered, meanwhile, the influence of EGR is also considered, the calculation precision of the fuel consumption rate is greatly improved, and the method has more advantages for calculating the fuel consumption rate under different working conditions.