The invention provides a device and a method for the synchronous accurate measurement of the transient flow field of a vane pump. The device comprises a test device system, a variable rotating speed work condition rotating shaft phase locking device and a PIV measurement system, wherein the test device system comprises a motor, a model pump, a pipeline system and a pressure stabilizing tank; the rear end of a motor shaft of the motor is connected with the model pump; the model pump is connected with the pressure stabilizing tank through the pipeline system; the variable rotating speed work condition rotating shaft phase locking device comprises a point light source laser, a moving disc and a point laser receiver; a plurality of round holes are formed in the circumferential outer edge of the moving disc; the moving disc is perpendicular to the motor shaft and fixed to the front end of the motor shaft; the point light source laser is positioned on the outer side of the moving disc, the laser receiver is positioned on the inner side of the moving disc, and the point light source laser and the laser receiver are positioned on the same horizontal line; and the PIV measurement system is connected with the variable rotating speed work condition rotating shaft phase locking device. The device can accurately measure and output the rotating speed parameters of the vane pump in the starting and stopping process of the vane pump and realize the data collection of the same phase transient flow field at different rotating speeds.