Based on the needs of development and research of high-speed motor-spindles, it can be concluded that a complex approach to this assembly is necessary as a complex mechanical system, which directly affects the behavior of the machine tool in exploitation. A complex approach should enable the thermal-mechanical behavior of machine tools to be predicted at the design stage. As the main spindles with high-speed rolling bearings are still the most represented construction solutions, the task of this work is to analyze the motor-spindle from the point of view of thermal-mechanical behavior, and to create a complex thermal-mechanical model of the motor-spindle assembly. On the example of a high-speed motor-spindle assembly, supported by ball bearings with oblique contact, it is desired to verify the defined model for the identification of thermal-mechanical behavior and analyze the influence of temperature on its static and dynamic characteristics through experimental testing. The work also analyzes the influence of different fluids for cooling the motor-spindle, as well as the influence of the amount of fluid flow both for cooling the stator and for cooling and lubricating the bearings. Starting from the global task defined in this way, the research in the paper is presented in nine chapters.