This thesis deals with simulation and experiment for axial displacements of spindle in spindle-bearing systems supported by angular contact ball bearings. High-speed spindle system inevitably experiences axial displacement due to thermal expansion and rotational speed-dependent characteristics of angular contact ball bearings. Such axial displacement in spindle significantly affects the accuracy of machine tools. In order to investigate the effects of major sources of axial displacement such as the axial pre-load, rotational speed and temperature. the axial displacement of spindle is measured under various conditions and also simulated with a developed program. The results from the simulation and experiment are of great use to predict or compensate axial displacements in spindles.