Abstract: Nanoscale tribological and mechanical properties of boric acid were studied by Atomic Force Microscopy (AFM) and Nanomechanical Testing System. The surface morphology, mechanical properties, and wear properties of boric acid on bulk boron oxide substrates in air at room temperature and various relative humidity ( RH ) were examined. It is shown that the growth of boric acid film is dependent on RH , and the growth rate of H 3BO 3 correlates with the micro wear rate of B 2O 3. The surface of B 2O 3 became soft with the growth of boric acid film.