Abstract: Coal/oil co-processing technology is an important way for clean and efficient utilization of coal and inferior heavy oil. Taking the recycle solvent, petroleum based heavy oil and lignite as the research objects, the effects of the concentration,solvent properties and ratio of two-component solvent (recycle solvent and heavy oil) on the viscosity-temperature characteristics of the coal-oil slurry were investigated. The liquefaction reactivity of the two-component solvent coal-oil slurry was studied, and the properties of the liquefied products were analyzed. The results show that the viscosity of the coal-oil slurry decreases rapidly to a lower value with the increase of temperature. Under the same conditions, the higher the concentration is, the greater the viscosity is. The viscosity-temperature characteristics of two-component solvent coal-oil slurry are similar to that of heavy oil-coal slurry, and the overall viscosity is lower than that of heavy oil-coal slurry. The higher the heavy oil content, the lower the viscosity rebound temperature and the larger the rebound range. When the heavy oil content is 30%, the viscosity rebound temperature is 240 ℃, and the rebounded range is the largest. Under the same viscosity requirement, the two-component solvent can prepare higher concentration of coal-oil slurry. In the process of coal/oil co-processing, there are synergistic effects, which optimize the transfer process of active hydrogen. When the content of heavy oil is less than or equal to 20%, higher oil yield and lower asphaltene yield can be obtained. With the increase of the proportion of heavy oil, the content of binuclear aromatics and long chain alkanes in the oil increases, and the distillation range increases.