Abstract: Since the effects of individual viscosity reduction were limited in the Tahe Oilfield, composite viscosity reduction technologies were discussed. Laboratory experiments showed that water-oil soluble viscosity-reducing agents could emulsify heavy oils with viscosity higher than 100×10⁴ mPa·s. The compound of heated and oil-soluble viscosity-reducing agents had better effects. Field works indicated that the chemical compound viscosity reduction could save light oils by 69.8%, and the heated and oil-soluble viscosity reduction could save light oils by 51.27%.