Abstract: Based on the characteristics of rod pump pumping and the indoor experiments,this paper has determined rheology of polymer solution applied in oil field,and have set up the equations of pump pressure,intake flow velocity,intake flow height,and discharge coefficient during suction process.Indoor experimental survey shows that during suction process the plot of pumping pressure vs.plunger displacement is basically concave-down and non-symmetrical parabolic type.In the case gas is present,velocity of pressure drop in pump increases.Practical examples on the spot has shown that pump's discharge coefficient is affected by the producing GORs,polymer concentration,submergence depth,stroke,stroke rate,pump diameter etc.,of the factors what have major effect is producing GORs,polymer concentration and submergence depth.Practical analysis in oil field is agreed with practice on the spot,which further verifies that this theory is right and reliable.