The invention discloses a method for precisely measuring wet gas. The method is characterized by comprising the following processes: establishing a correction mathematical model of the wet gas and a database of the relationship between temperature t and absolute humidity f; compiling a computer program for the mathematical model and the database and placing the mathematical model and the databaseinto a flow meter CPU chip; connecting a temperature detector (3), a pressure detector (4) and a pressure differential detector (5) of a flow meter (6) to a measuring pipeline (1) respectively to detect temperature, pressure and pressure differential signals; performing analog-to-digital conversion to convert the temperature, pressure and pressure differential analog signals into digital signals and inputting the digital signals to a measuring computer (8) through a communication controller (7) by the flow meter (6); and calculating correction values for the correction model and correcting a measuring result by the measuring computer (8). By using computer technology, the method realizes the timely compensation of the temperature, the pressure and the humidity and solves the problem of inaccurate measurement of the wet gas completely.