The tribological properties of a lithium calcium complex grease based on calcium sulfonate complex and lithium complex greases are investigated. The tribological properties of the latter greases are compared using an Optimol SRV reciprocating friction and wear tester. The morphologies of the worn surfaces are traced by a scanning electron microscope (SEM) and the chemical states of several typical elements on the worn surfaces are examined by x-ray photoelectron spectroscopy (XPS). The results indicate that the new grease has a low friction coefficient and good wear-resisting ability. This is attributed mainly to tribochemical reactions between the grease components and the friction surface with formation of a film that includes CaSO (3) , CaCO (3) , and CaO as well as compounds of lithium, boron, etc.