Lithium complex greases prepared from poly-α-olefin synthetic oil,intermediate base mineral oil,paraffin base mineral oil,and their proportional combination as base oils were taken as the research objects.The effects of base oils on the physical and chemical properties,microstructures and rheological properties of lithium complex greases and their correlation were investigated.The results show that there is a corresponding relationship between the microstructures and properties of lithium composite greases.The structure regularity and continuity of the composite lithium base soap fibers prepared from poly-α-olefin synthetic oil are poor,but their thixotropic and viscosity-temperature properties are superior.The soap fibers of the composite lithium greases prepared from intermediate base mineral oil are of higher regularity.Their greases have the strong structural stability,but poor viscosity-temperature characteristics.The soap fibers of the composite lithium greases prepared by the combination of synthetic oil and mineral oil are slender and uniform with high regularity,and these composite lithium greases are of strong structural stability,good colloid stability and shear resistance.