Abstract: Crude oil in China mostly have high waxy and solidifiable behavior.generally, the heated oil transportation process is adopted to handle these viscous crude oil.The technique of forward transportation and reverse pumping is sometimes necessary in the condition of low throughput.However, this kind of technique is neither economy nor safety due to its complicated operation and big fuel oil consumption.According to the physical and chemical properties of crude oil and the interaction mechanism between depressant and wax, analyses for compositons and contents of wax, microwax, gum and asphaltene in the crude oil have been made by China Oil and Gas Pipeline Science Institute (PSI).A reasonable synthesis ratio is selected among various materials according to the characteristics of depressant and wax which are eutectic and adsorbable.By means of laboratory tests, pilot testing and amplification tests with the polyaction condition strictly controlled, the GY-2 oil depressant has been synthesised by PSI.It is proved that this depressant has remarkable effectiveness of reducing the pour point and viscosity of crude oil.