The principle of calibration for gas flowmeter with tracer gas dilution method is introduced, and experiments on calibration for gas flowmeter in a 0.300m internal diameter and 90 degree bent pipe are presented, which CO and air were selected as tracer gas and gas stream. The sampling points were downstream of the bend pipe around 9D (D is the internal diameter of pipe),12D and 15D, respectively. The results show that the radial and axial mixing between tracer gas and air have been uniformed downstream of the bend pipe at the sampling point of 12D and 15D when the flow rate above 3.2m/s, and the relative error of the flow rate calibration attains the level of 4.3%. The calibration accuracy depends on the tracer gas injection flow rate, tracer gas concentration at the sampling point, and the uniformity of tracer gas concentrations downstream at the sampling point. Calibration for gas flowmeter with tracer gas dilution method is feasible, and it provides a method for industrial gas flowmeter calibration in pipeline transportation.