The mass method is a method of weighing the mass of the fluid flowing into the container within the measurement time to obtain the flow rate. When calibrating, use a pump to draw the test fluid from the liquid storage container through the flowmeter to be calibrated and then enter the container containing the liquid. Measure the temperature of the fluid while weighing it out. It is used to determine the density value of the measured fluid at this temperature. The volume of the fluid can be obtained by dividing the weight of the measured fluid by the density of the fluid at the measured temperature. Compare it with the volume indication (accumulated pulse number) of the meter. The meter constant and accuracy of the flowmeter to be calibrated can be determined. The accuracy of this method system can reach 0.1%