Abstract: The conventional oriffice flowmeters, though accurate enough to meet such standards as GB2624-81 and SYL04-83, practically fail to reach their precision due to unqualified design, fabrication, installation and application of the restriction devices.Based on the analysis on such factors as working principles and installation requirements for oriffice restriction device, instrument selection, pulsation flow, etc., the writer points out that the essential factor debasing the precision of oriffice flowmeters is the deviation from design of the geometric structure of restriction device and of the flow state.Some parameters, such as gas density, flow expansion coefficient, flow coefficient, etc., shall be corrected so as to keep the flowmeter operate under normal conditions.In addition, automatic, continuous integration or a dedicated computer processing shall be adopted to maintain the measurement precision with minimum error.