In this article, Lewis acid-base complex of lithium 12-hydroxystearate (LHS) with diboron compound is formed by the introduction of bis(pinacolato)diboron (B(2)Pin(2)) into lithium grease. The interaction between Lewis acid B(2)Pin(2) and Lewis base RCO2- of LHS is characterized by various techniques. Moreover, the rheological and tribological behaviors of the base grease are evaluated at low and moderate temperature. The results indicate that the addition of B(2)Pin(2) can noticeably enhance the rheological property of the base grease because the formation of Lewis acid-base complex is beneficial for improving the soap fiber structure strength, and B(2)Pin(2) could also help reduce the friction and wear of the grease during the sliding process, which likely owing to the boundary lubrication film generated by B(2)Pin(2) adsorption on the rubbing surface and tribochemical reaction between borate esters and steel surfaces. The improvement of mechanical stability and tribological properties is beneficial to increasing the grease service life.