Angular contact ball bearing used in machine tool usually works under high speed and light load condition. Proper preload on bearing can decrease temperature rising and prolong life of bearing. In order to illuminate the effect of preload on thermal and dynamic characteristics of bearing, preload experiment of rolling bearing with oil-air lubrication is studied in this paper. Comparison of position preload, pressure preload, and intelligent preload methods are investigated, results shows that intelligent preload method can ensure high stiffness and low temperature rising of bearing for large range of speed of bearing system.