Abstract: The density, viscosity and heat capacity of waxy crude oil is changed along with the temperature drop and flow type and the flow patterns are different along the pipe during the design and operation. Considered the above factors, the pipeline is divided into some nodes to calculate the steady temperature drop.Take the latent heat of wax crystallization into account, the equation of the transient temperature is deduced under the condition of less change of rate of flow based on the energy equation, and resolved by the three-characteristic line method.This method is of high calculation precision, which can be taken as a theory foundation of design and simulation of pipeline.