To measure the parameters of fiber and to visualize the reshaping process of fiber in air tunnel,an experimental approach is developed in the present work.The tunnel is designed with gradient flow velocity,and the fiber reshaping images as well as the fiber length value are obtained experimentally.An analytical expression of velocity distribution in the tunnel is theoretically derived and the simulated results are obtained.Automatic fiber reshaping including stretch and rotation is verified using the dynamical equation and the multi-spherical chain model.It is shown that pull force by air flow makes a chain of balls become straight and Stokes moment makes the ball chain rotate.Finally,reshaping criterion related with flow velocity is formulated.