Abstract: During the modelling for optimizing the production parameters of progressive cavity pump wells using the nodal system analysis, both discharge port pressure and suction pressure need to be calculated in order to further choose progressive cavity pump and design rods according to pressure difference. To calculate discharge port pressure, this article considers the influence on frictional pressure drop in the gas and liquid two-phase flow between rod and tubing owing to rotation of rods. To take GLB40-42 progressive cavity pump for an example, the analysis and calculation show that pumping rod diameter and rotational speed have great influences on the frictional pressure drop. Therefore this affords convincing foundation for further optimizing progressive cavity pump and rods.