Abstract: By studying the principle of lobed rotor meter and its elements' properties, puts forward a new view for the role name of lobed rotor and confirms flow problem of lobed rotor meter again applying practice and experience. In leakage detection practice, quintic average value method of transient flow is used to eliminate the deviation caused by repeated metering so as to increase the sensitivity in pipeline leakage detection. Revising the error between transient flow and integrated flow with flow coefficient can increase positioning accuracy in pipeline leakage detection evidently.