While the number of test meters increases and the water body of tank fluctuates， the principle of flow meter test and calibration do not match. The result may lead to system errors. These errors are difficult to find and there are no standardized?criteria?for?assessing. This paper ana - lyzed the mechanism of the meters， which indicates that the speed of the instrument can be detected by the torque meter by starting speed V0 at low speeds， and its speed linear formula can be revised by a standard value. At medium and high speeds， the dry test， hydraulic screw pitch test， integral test and optimized one-speed level calibration can be introduced， which also can be used to verify the flow meter calibration formula at hydrometry stations.