Steam generator is an important equipment of nuclear power unit, and its flow rate is directly related to the operating power of the unit. Accurate flow measurement and monitoring is an effective prerequisite to ensure stable and long-term operation of the unit. However, when the pressure taking system is used to measure the steam-flow rate, the phenomenon that the flow indication number is abnormal but the actual flow rate does not change occasionally often occurs, which affects the normal production operation. Based on the principle of differential pressure method, this study studied the influence of flow resistance and flow characteristics of waveform plate steam separator, an important part of steam generator, on flow measurement, and completed the analysis of waveform plate flow field and the establishment of benchmark model through numerical simulation. The uncertainty quantization method based on Morris One at A Time (MOAT) was used to analyze the sensitivity of the deviation factors affecting the accuracy of flow measurement at the waveform plate. By comparing MOAT mean and MOAT standard deviation, it is found that the assembly inclination angle of the corrugated plate is the most important factor affecting the measurement accuracy of flow rate, and should be the key check item during the maintenance of steam generator.