The invention discloses a three-dimensional atom probe sample preparation first-stage polishing device. The three-dimensional atom probe sample preparation first-stage polishing device comprises a base, a supporting plate, a liner plate, an eccentric wheel, a first lever, a second lever, a connecting rod, a fixed plate, a stand column, a motor and a bolt. By adopting the polishing device, the manual polishing process is changed to the mechanical polishing process, so that the manpower is saved, and the precision is improved. The rotation of the motor is converted to the up-down movement through the levers and the eccentric wheel, and the application requirement can be met. By adopting the polishing device, the spatial position of the preparation of samples in different sizes can be adjusted, and the flexibility is strong. By adopting the aluminum alloy material, the weight is reduced, and the cost is reduced. The polishing device is electrified to execute the electrochemical polishing, so that the polishing size is fixed, the precision is high, the sample quality is good, the taper is large, and convenience in observation of the three-dimensional atom probe and data acquisition can be realized. A simple mechanical device capable of rapidly preparing a sample is provided for preparing a three-dimensional atom probe metal sample.