Investigation on the law of tribological modifying activity influenced by structure of additives will make prediction and design of materials tribological behaviors possible.Four types of diamine Schiff base Cu(II)complexes as additives for modifying UHMWPE are synthesized,they are respectively:Cu(II)complex with ethlenediamion-N,N′-bis(salicylidene),Cu(II)complex with 1,6-hexanediamine-N,N′-bis(salicylidene),Cu(II)complex with 1,2-cyclohexanediamion-N,N′-bis(salicylidene)and Cu(II)complex with 1,2-phenylendiamion-N,N′-bis(salicylidene).Friction coefficient of the modified UHMWPE/Ti6Al4V is studied using a reciprocating friction and wear tester between line/surface contacts sliding in reciprocating under the condition of boundary lubrication with 25 vol% calf serum deionized water solution,at the same time volume loss of wear of the polymers is measured.3D topographies of the worn surfaces of the polymers and images of the worn surfaces of titanium alloys against the polymers are investigated respectively by CWLM and SEM.How the structural unit R of Schiff base copper complexes in the modified UHMWPE influences their tribological modifying activity is also discussed.Results show that the smaller the group R is,the higher the modifying activity is obtained,and the open chain is more reactive than that of alkyl and aromatic ring.Therefore,the Cu(II)complex with ethlenediamion-N,N′-bis(salicylidene)has the highest tribological modifying activity as its R group is the smallest and open. Investigation on the law of tribological modifying activity influenced by structure of additives will make prediction and design of materials tribological behaviors possible. Fu types of diamine Schiff base Cu (II) complexes as additives for modifying UHMWPE are synthesized, they are respectively: Cu (II ) complex with ethlenediamion-N, N’-bis (salicylidene), Cu (II) complex with 1,6-hexanediamine- N, N’-bis (salicylidene), Cu (II) complex with 1,2-cyclohexanediamion-N , N’-bis (salicylidene) and Cu (II) complex with 1,2-phenylendiamion-N, N’-bis (salicylidene) .Friction coefficient of the modified UHMWPE / Ti6Al4V is studied using a reciprocating friction and wear tester between line / surface contacts sliding in reciprocating under the condition of boundary lubrication with 25 vol% calf serum deionized water solution, at the same time volume loss of wear of the polymers is measured. 3D topographies of the worn surfaces of the polymers and images of the worn surfaces of titanium alloys against the polymers a rearchers respectively by CWLM and SEM. How the structural unit R of Schiff base copper complexes in the modified UHMWPE influences their tribological modifying activity is also discussed. Results show that the smaller the group R is, the higher the modifying activity is obtained, and the open chain is more reactive than that of alkyl and aromatic ring. Before, the Cu (II) complex with ethlene diamion-N, N’-bis (salicylidene) has the highest tribological modifying activity as its R group is the smallest and open.