Abstract: Dynamic metering is an important way to measure oil flow, and errors shall be reduced as much as possible to achieve accurate measurement. Analysis on the errors in dynamic metering is made based on the theory of error, and concludes that the main contributors to the errors come from densimeter, water cut meter as well as flow meter. Error reduction can be achieved by improving the precision of flow meter, thermometer, water cut meter and densimeter, by reducing sample oil's deviation, and by correcting flow meter with specific factors. It is suggested to adopt dynamic sampling and phyical examination, to realize continuous on line measurement of oil density and water cut, to choose proper sampling interval and to calibrate the flow meter on line.