The energy conversion device with flexible blades was taken as the research object; in the closed experimentation section of the low speed wind tunnel, velocity field of curved blade boundary layer was tested by PIV measure technology; when camber of the blades was changed, the rule of flow separation and vortex motion on the boundary layer were obtained. The experimental results showed that the bending deformation of blades in the front layer can reduce accumulation and diffusion low-energy fluid on the boundary layer, and it is helpful to reduce the lift loss of the blades due to flow separation; but for the rear layer, flow instability will increase because the dynamic stall vortex near boundary layer extends due to the bending deformation of blades.The flow field analysis of the curved blades can guide material selection and the design of flexible blades, and provide experimental reference for improvement of the energy conversion efficiency and working stability.