Abstract: The oil metering and regular calibration of flowmeter are important work for petroleum transportation and petrochemical enterprises. This paper describes the application of UF-Ⅱ bi rotor flowmeter and technical improvement of LJG-22 prover. The advantages and disadvantages of Roots flowmeter, blade flowmeter and bi-rotor flowmer are examined and analyzed. Combined with the field application and proving/data comparison of flowmeter, the UF-Ⅱ bi-rotor flowmeter is taken as a major metering apparatus for oil transportation in the 1st Oil Production Plant of Jiangsu Oilfield. The technical improvement on the prover is made. A new type motor-driven cross valve and automatic control system for LJG-22 prover is developed, which is helpful to the proving efficiency and quality of flowmeter calibration.