Abstract: For Christmas tree pipeline, U-Class temperature, 69 MPa design pressure in 1 500 m water depth, the crude oil temperature drop at pipeline center calculated with finite element method is amounted to 41.73% in 1 hr without heat insulation. The paper calculates the total cost per unit volume of insulation materials and insulation effect of monolayer insulation and double layer insulation design for the pipeline. The results show that under the same conditions, the crude oil temperature in the center of pipeline with monolayer insulation and double layer insulation falls by 0.79% and 0.25% respectively. For the pipe insulation material per unit length, compared with the monolayer insulation, double layer insulation needs more 0.072 534 m³ than that of the former, but saves insulation materials cost and decreases a 3.022 RMB/m of heat loss cost annually, so double layer insulation is more economic.