A test device suitable for acceleratory oblique water entry of a wedge has a frame, a water tank placed below the frame, an accelerator installed above the frame, an obliquing device connected to the frame, a wedge connected to the obliuqing device and an observation system. The frame is provided with vertical slide rails and a transverse slide rail. The accelerator mainly includes an air cylinder and an air compressor. The wedge is a flexible wedge or a rigid wedge. The observation system includes a pressure sensor, a strain sensor, a velocity sensor, an acceleration sensor and a particle image velocimetry device. The repeatability of the test process can be ensured by controlling the output pressure of the air cylinder.