Abstract: In this paper, research is conducted in respect of viscosity/drag reduction to solve the problems in heavy oil pipeline transportation. Pipe flow experiment and rheometer test are used together to reveal effects of heating, gas injection and dilution on heavy oil viscosity/drag reduction. Research results show that, for the heavy crude oil with Newtonian fluid constitutive relation, both heating and dilution have significant impacts on viscosity/drag reduction, which may decrease exponentially. For gas injection, drag reduction only happens under the condition of large flowrates or at low temperatures, but viscosity does not decrease greatly. Furthermore, for the dilution, an exponential equation is developed to predict viscosity of heavy crude oil and light oil mixture. The equation is a function of heavy oil viscosity, light oil viscosity and volumetric content of light oil. Comparison with test data may confirm accuracy of the prediction deducted by using the equation.