Abstract: Considering the effect of oil transportation temperature on oil viscosity and the oil viscosity and flow—rate on pump efficiency, flow regime and economic pipe size, using the sum of the shared COSt per year of pipeline and thermal insulation engineering construction investigation, the maintenance cost Per year of the pipeline, the electric power and heat power consumption cost per year in pipeline running as the object function, a complete calculation model for economic pipe size of buried heated oil transportation pipeline is given in the paper.The model can satisfy oil temperature drop constraint condition along the pipeline automatically, suitable for crude oils with different viscosity—temperature characteristicS, different thermal insulation materials and the pipeline of different burying depth.A calculation is carried OUt with the model applying Fibonacci Search Algorithm and results show that the model can reflect various factors well tO the impacts on the economic pipe size and provide a theoretical basis for optimized technological design of buried heated oil pipelines.