The invention discloses an on-spot detecting method and a device of a family in-use gas meter. In the method, a meter front manometer, a thermograph, a standard gas meter and a meter back manometer are connected in series between a user gas meter and a cooker; a meter front valve and a meter back valve are opened and a stove front valve is closed for safety detection; after the safety detection, the stove front stove is opened, the stove is ignited, a small fire combustion mouth is ignited, a flow adjusting device is adjusted to a smallest flame for detecting the basic small flow error, then the small fire combustion mouth and a middle fire combustion mouth are ignited, the flow adjusting device is adjusted to a middle flame for detecting the basic middle flow error, and simultaneously the small fire combustion mouth, the middle fire combustion mouth and a large fire combustion are ignited, the flow adjusting device is adjusted to a large flame for detecting the basic large flow error, and an air through flow is over 50 liter in every detection. The device and the method can in-site detect the safety and the basic error of the family gas meter under in-use environment. The device and the method have the advantages of quick speed, short time, low cost, easy operation, safety and accuracy.