The lubrication mechanism of the zinc phosphate film derived from ZDDP was studied using genuine computational chemistry methods, i.e., NEW RYUDO code, a hybrid quantum chemical/classical molecular dynamics simulation, and a vibrational spectrum simulator. Using the NEW-RYUDO program, the dynamic behavior of the wear particle was observed. The deformation of Fe2O wear particle during simulation along the friction direction was observed at the simulation time of 250 psec. Several Fe atoms in the wear particle migrated into the phosphate matrix at 500 ps. The phosphate matrix digested the FeO wear particle due to their interfacial chemical reaction. The anti-wear mechanism of ZDDP-derived film was based on the digestion of wear particles due to wear during the friction process. This is an abstract of a paper presented at the Proceedings of World Tribology Conference (Kyoto, Japan 9/6-11/2009).