Abstract: The study on the air patterns in the human upper respiratory tract plays a very important role in investigating the aerosol deposition in the human upper respiratory tract.PIV (Particle Image Velocity) technology was used to study the steady flow in the human upper respiratory tract.The results show that the airflow velocity is high in the middle and lower part of the oral and low in the other part.The airflow velocity increases at the outer wall of the pharynx.The airflow with the high velocity flow downstream anear the inner wall of the larynx and the trachea with the high velocity zone appearing near the inner wall of the larynx and the trachea.The shearing strength acting on the outer wall of the pharynx,the inner wall of the larynx as well as the trachea are high,which endure the high load,finally may lead to the wall strain and tissue injury at these zones.