The unbalanced quantity of highspeed rotating micro turbojet engine in rotor system has especially effects on working state of the rotor. On the premise that gyro is effective, the variations of bearing dynamical reaction in the micro turbojet engine with the rotating speed and unbalanced quantity distribution azimuth angle are studied by using harmonic response analysis method. The results show that the greater the rotating speed is, the greater the bearing dynamical reaction, and the influence of the magnitude of unbalanced quantity on bearing dynamical reaction is greater than that of rotating speed. The bearing dynamic reactions in the position of compressor and turbine are of maximum and minimum at unbalanced quantity distribution azimuth angle of 180° respectively. The results of analysis provide an important reference for decreasing the vibration problem of engine and avoiding bearing damage caused by unbalanced quantity.