Abstract: To study the effect of flow deflector angle on the hydrodynamic performance of otter board, a flume model experiment was conducted to measure the lift coefficient (C_L), drag coefficient (C_D) and lift to drag ratio (K) of two flow deflector vertical cambered otter boards, each with three kinds of flow deflector angle. The experimental results show that: 1) For the single flow deflector vertical cambered otter board, when the angle of attack was between 20°~35°, the C_L and C_D values showed a downtrend with increase of flow deflector angle. In this case the otter board D1 (flow deflector angle was 35°) showed better hydrodynamic performance. 2) For the double flow deflector vertical cambered otter board, when the angle of attack was between 25°~35°, the otter board S3 (the front flow deflector angle was 20° and the middle flow deflector angle was 25°) showed better hydrodynamic performance. It is suggested that the best working scope of angle of attack of otter board D1 was between 15°~30°, in that case, C_L>1.2 and K>2.0;the best working scope of angle of attack of otter board S3 was between 20°~30°, in that case, C_L>0.8 and K>3.0. The critical angle of attack of lift coefficient increased with increase of flow deflector angle. Properly regulating flow deflector angle could optimize the hydrodynamic performance of otter board.