Abstract: Based on the design practices worldwide, and considering the actual demands, Sinopec innovated a mobile gas flowrate calibration equipment. The equipment can be used to effectively calibrate gas flowmeters and supplement the gas flowrate traceability and transmission system. It is designed, for the first time, with three standard braches and the working flowrate range from 20 m³/hr to 8 000 m³/hr. A high-accuracy turbine flowmeter is chosen as the standard, and an ultrasonic flowmeter for verification. Advanced forcible seal ball valves and axial-flow control valves are installed to close branches and control flowrate. By uncertainty evaluation and testing, the equipment is proved with an uncertainty less than 0.33% (k=2), fully meeting the design requirements.