Abstract: The accurate metering of the oil well effluent is the major premise to higher recovery efficient, also is the basis to stable oil production and high-yield in oilfield. There in-line water cut metering methods for oil well are introduced, which are analyzer installed on the two-phase separator with flow meter; densimeter with the same device as the said above, and analyzer installed on the triphase separator with flow meter. The comprehensive errors in the measure of the daily output of crude are analyzed respectively. By determining δB, the sampling error in the error formula for oil well metering, δF, , the additional error for operational conditions and the value collected for the water cut analyzer during metering, it concludes that the first method is not practical to reach the current standard issued by CNPC in metering accuracy; the second method is also difficult to come up to 5% in comprehensive error for the oil with high water cut in oil metering; while the third method can increase the metering accurately with its metering error less than ± 5%.