A new multi-physical coupled dynamic model of high-speed motorized spindles is established in the paper. The entire model consists of four sub-models: bearing, thermal, spindle dynamic and electromagnetic models. Based on the coupled relationships, five coupled factors, which are thermal expansion, centrifugal expansion of bearing inner ring, contact expansion of bearing ring, the unbalanced magnetic pull and centrifugal force, have been presented. And the effects of coupled factors on the operation states of motorized spindles could be acquired from the designed solution procedure. Finally, an overall experiments and calculations on a 2ZDG60 motorized spindle are carried out under several operating conditions. Calculation results show that the coupled factors have great influence on dynamic stiffness and loss power of the bearings, dynamic behaviors of the spindle, respectively. The good agreement between the theoretical results and the experimental data indicates that the multi-physical coupled dynamic model is capable of accurately predicting the dynamic behavior and temperature rise distribution of high-speed motorized spindles.