Abstract: The mass of product oil at retail is generally taken from the calculations through the method of volumetric flow/density inspection. However, this method, which is prone to influences from many factors, may produce a considerable error. Only mass flowmeter can avoid the factors, and increase the metering accuracy. The paper introduces the application of E+H mass flowmeter introduced from Germany by Shiji-azhuang Oil Refinery. Problems on the application of mass flowmeter are analyzed from installation, operation, measuring range and operation environment. The best installation way the paper considered is vertical; if installed horizantally, the outlet end of the meter must be a 1~2 m long straight-line segment, and a gauge pressure of 20 kPa maitained. The heavy metering error will be produced with the product oil e-vaporated passing through the flowmeter, so, the back pressure of flowmeter has to be increased to reduce evaporation and avoid vibration of flowmeter.