Abstract: The viscosities for Shengli crude oil and imported crude oil mixed at different proportions and temperatures are systemically studied. The two crude oils are transported through Linyi-Yizheng Oil Pipeline. A new method derived the proportion of mixed oil from its viscosity is presented. The deriving principle is that at first measures the viscosity for the mixed oil with different proportions and temperatures, and then regresses the relational expression for the proportion of mixed oil vs the viscosity and temperature of mixed oil, and at last calculates the proportion of mixed oil with the regression expression. The calculation results can provide a safe operation fundament for the pipeline.