Abstract: A mobile，multistage and skid-mounted oil well metering device is developed for the traditional measurement can ′t meet the needs of yield test of each oil well in the process of production，especially，it can′t survey or record gas production at test stage and is difficult to implement accurate measurement in rather wide measurement range.The structure，operation principle，key technical indexes，systematical composition，key problems in technology and consideration for design are introduced.Based on the traditional technology and empirical foundation，several key technologies，such as high efficient gas-liquid spiral flow and separation，high efficient multistage liquid-liquid spiral flow and separation，emulsion breaking technology，improving the pure oil measuring accuracy by multi- time settling out，the unload technology of the metering separator and the selection criteria of the optimum flow measurement are presented.Two issues are studied in detail，which are how to improve measuring accuracy by exploding emulsified water to enhance separating effect at the series cyclone time，the problem of the parameter control mode is seriously considered，the primary factor is either underset or overfall.

Key words: mobile, multistage separation, metering device, gas-liquid separation, oil-water separation