Flow metering of multiphase pipeline is an urgently problem needed to be solved in oilfield producing in China. Based on the principle of multiphase oil and gas flow in the open channel, four liquid metering models(Falling Model I, Falling Model II, Open Channel Model and Element Resistance Model) and one gas model were obtained to calculate the gas and liquid flow rate, in which the water cut was measured by the differential pressure. And then a new type of multiphase meter system was developed based on these models and neural networks were developed to improve the estimating results of gas and liquid flow rate with the new metering system. At last a lot of experiments of multiphase metering were finished in lab and field. According to the experiments, the results of the metering system show that the liquid flow rate error was no more than 10%, and gas flow rate error was no more than 15%, which can meet the demand of the field flow rate measurement. Furthermore the relationship between liquid and gas fl...