Abstract: Influences of normal load, sliding speed and sliding duration on friction coefficient of ultrahigh molecularweight polyethylene (UHMWPE) modified by 5%, 10% and 15% copper (II) complex in mass fraction of bissalicylaldehyde-ethylenediamine (Schiff base copper (II) complex) respectively were investigated on a microtribometer in a speed range of 50~1600μm/s under conditions of dry friction and vegetable oil lubricated condition. A 100Cr6 steel ball was used as counterpart. Pure UHMWPE was also tested as a reference. Results showed that the friction coefficient of modified UHMWPE with 5%~15% (mass fraction) Schiff base copper (II) complex was independent from normal load at low sliding speeds in dry condition or using vegetable oil as a lubricant. And it was much lower than that of pure UHMWPE, i.e. the friction coefficient of all modified UHMWPE in dry condition had a 29% reduction as compared to that of pure UHMWPE. The results also showed that the effect of sliding speed on friction coefficient under the lubricated condition could be decreased as the content of Schiff base copper (II) complex in the modified UHMWPE was high enough, e.g. 15%. The results showed that the friction coefficient of modified UHMWPE with 5%~15% Schiff base copper (II) complex was independent from sliding speed and sliding duration under dry condition. The stable friction coefficient of the modified UHMWPE at low speeds under dry sliding can meet the requirement of frictional pair for the nanopositioning application.