Abstract: An experimental study was performed to investigate the deflection of film trajectory on a flat blade model under the rotating operating conditions.The moving trajectory of film was mainly governed by the inertial force and radial pressure gradient in the blade passage.A new dimensionless parameter Φ,which is related to the ratio of the above two forces to determine the radial deflective angle of the film trajectory,was demonstrated in the present study.The steady-state thermochromic liquid crystal(TLC) technique was employed for flow visualization,and all the signals from the rotating reference frame were collected and transmitted to the stationary receiver via a wireless launcher,which was fixed in the rotation laboratory bench.The experimental results demonstrate that the spanwise deflection of film trajectory decrease with the increase of Φ values.