At the time of using the mechanical air-flow meter to measure air velocity in tunnel and air duct, all air-flow meters are provided with the corresponding air velocity rectifying curve respectively so as to make use of rotation speed of the air-flow meter to find the real air velocity corresponding to the measured location. The air velocity rectifying curve for the air-flow meter was determined according to the air-flow meter inspection done on the air tunnel type air-flow meter checkout instrument in the laboratory. Based on performance features of the mechanical air-flow meter, the regression model for the inspected data is monadic linear model. However, it could not be clear whether the inspected data can really reflect a correlative linear relation of air-flow meter rotating speed with real air velocity, so the inspected data are required to receive the significance check at the given inspecting accuracy according to the features of monadic linear regression. Only through the significance check, can the rectifying curves for air-flow meters and the rectifying equation, which have been presented, be used for practice in air measurement of tunnel and air duct.