Abstract: Using the sum of the end value expense which contains thermal insulation project investment, electric power and heat power consumption as object functions, a new mathematic model for calculating economy insulation thickness of buried heated oil transportation pipelines is set up. In the model, oil properties, pipeline laying depth, oil inlet temperature and the time value of expense are considered. Calculation case shows that pipeline laying depth obviously influences the economic insulation thickness and the influence must be considered in insulation design of buried oil pipeline. For the pipeline of small-diameter, longdistance or great flow-rate, the effect of electric power consumption on economic insulation thickness should be considered in the pipeline design.