Abstract: Factors influencing on loss and gain of quantity in distribution of refined oil products are analyzed. To solve this problem, estimation method and judgment of the quantity of loss and gain, seal function and sealing process are mentioned in the paper. It is presented that error metering is a major factor in metering disagreements and also the key in establishing loss and gains standard. Based on different error confirming way in metering, standard error method, actual error method and uniform error method may be used to confirm loss and gain standard. It is considered that each system error applied by uniform error method is the actual error in testing calibration of a same metering system.