In order to avoid conducting complex viscosity test of formation heavy oil，simplify the solving process of PR viscosity prediction model and finally improve the applicability of prediction model，a viscosity prediction model of Gubei heavy oil was established based on correction of acentric factor. Based on dehydration，blending tests and viscosity tests under different water cuts of heavy oil，the viscosity correlation of ground degassed crude oil viscosity with water cut and temperature for PR equation was established to simplify the related viscosity experiment. It can also be used to improve accuracy of PR viscosity prediction equation by correcting the calculation error of Edmister acentric factor. The viscosity prediction model of Gubei1-38 heavy oil was established for numerical simulation taking environment parameters of formation heavy oil with multi-factor and multi-level as initial conditions. The test and calculation results show that high content of heavy fraction results in the increase of formation pressure，and viscosity reduction effect is not obviously related to the light fraction，while temperature，water content and gas-liquid ratio is the main influencing factors of viscosity of the formation heavy oil.