The invention provides a fresh air mass calculation method of a double-VVT boosting direct-injection gasoline engine. The fresh air mass calculation method of the double-VVT boosting direct-injectiongasoline engine comprises the steps that the relative mass of total gas in a cylinder is determined based on the ratios of the pressure, volume and temperature of the total gas in the cylinder to thepressure, volume and temperature under a standard condition; the relative mass of waste gas left in the cylinder is determined based on the ratios of the pressure, volume and temperature of the wastegas left in the cylinder to the pressure, volume and temperature under the standard condition; the relative mass of backflow waste gas in the cylinder is determined based on the ratios of the pressure, volume and temperature of the backflow waste gas in the cylinder to the pressure, volume and temperature under the standard condition; and the difference value obtained by subtracting the relative mass of the waste gas left in the cylinder and the relative mass of the backflow waste gas in the cylinder from the relative mass of the total gas in the cylinder is used as the fresh air mass in the cylinder. By adoption of the fresh air mass calculation method of the double-VVT boosting direct-injection gasoline engine, the influences of constants, correlated with the physical property, in an actual gas state equation can be weakened, and thus, the calculation precision of the fresh air mass in the cylinder is improved.