Abstract: It is often necessary to know the mixture viscosity when pipeling transporting heavy oil by blending with a light one to have it diluted. The article, based on Einstein's indefinite dilution theory, induces a power equation, and presents with reference to literature and information concernd a few formulas to calculate the mixture viscosity. It is concluded that the mixture viscosity can be obtained by calculation with Ladar Equation so long as the density, viscosity and volumetric composition are given, which is very simple in application.