For the highpressure descaling system of plate mill, using air thermodynamics, fluid mechanics and heat transfer, a theoretical analysis was carried to the airpipeline heating of the accumulator, improvement measures were proposed according to the analysis results. Theory research shows that the outlet temperature is higher than the design value, the main reason is that the flow velocity is too quickly, coming into a high heat transfer coefficient in the innersurface of airpipeline. Practice has proved that the reasonable diameter of the airpipeline can successfully solve the problem of high temperature, in accordance with the quantitative analysis results.