Abstract: Detailed analysis was conducted on the strength of the gear keys of an air compressor rotor. The distribution of stresses in the key and the pressure stresses on the touching surface was obtained by taking the most unfavorable condition that there is only one key touches the keyslot into consideration. Also analyzed was the vibration characteristics of the blades of the rotor turning at high speed. The results show that the distribution of the maximum equivalent stresses is dependent on what sections of the key touch the keyslot. Nevertheless the dynamic characteristics of vibrations is normal regardless of the touching conditions.