The film cooling performance of the suction side of a turbine blade is experimentally and numerically investigated under the rotating condition. Experiments were performed on a 1.0-stage turbine. In the experiments, the effects of density ratio (0.96 and 1.52) and blowing ratio (0.2-1.0) were studied. The rotational effects were studied by comparing results of three mainstream rotating Reynolds numbers (3528, 4410 and 5292). Three hole positions of 1/4, 1/2 and 3/4 of the total blade height were set on three blades to confirm the mainstream influence. The jets of the holes at 1/4 and 3/4 of the blade height deflect to the mid-span of the blades. The film protection at both hole positions is damaged by the mainstream vortices, resulting in a lower cooling effectiveness. Moreover, as proven by the flow field, the passage vortex influence can be strengthened by the rotation. Thus, as the rotating Reynolds number increases the film cooling performance worsens. An optimal blowing ratio, 0.6, for the mid-span hole film cooling exists. Different from the flat plate film cooling, the film deflection occurs in the blade film cooling and decreases as the blowing ratio. At last, the high density ratio can improve the film cooling performance. (C) 2019 Published by Elsevier Ltd.