Abstract: In actual depressant crude pipeline transportation, a crude sample is transported in tight line with pressure. In simulation test of depressant crude pipeline transportation in non -tight line state for a long time, there exists a phenomenon of light component volatilization. Analyzes the influence of light component volatilization on low temperature viscosity and crude pour point of depressant crude. Volatilization of light component sharpens the affect of medium and low viscosity shear action, that is adding proper amount of light oil can improve anti-shear property of depressant crude. Therefore, tight pressure tanks shall be used in simulation test of pipeline flow shear during slow drop in temperature.