Using the vehicle turbocharger with a floating ring bearing as the research object, the airflow exciting forces of sealing structure and blade tip clearance were calculated according to Alford and Black model. The finite element models considering and without considering airflow exciting forces were built. Then the critical speed, steady response and transient response of turbocharger rotor system were acquired and were analyzed through the comparison between them. The results show that the airflow exciting forces lead to the tangential force of rotor forward vortex so that the amplitude of rotor vibration becomes large and the stability of rotor becomes poor. In addition, the magnitude of rotor vortex increases with the increase of speed. The airflow exciting force of blade tip clearance has a great influence on the stability of rotor system.