The disclosure provides an electrode plate and a surface treatment method thereof. The surface treatment method firstly adopts a special annealing process to process the electrode plate to form a Mg film on the surface of the MgAl alloy material layer, and then make the Mg film chemically react with the fluoride ion to form a MgF2 film on the surface of the Mg film or the Mg film is converted into a MgF2 filmentirely. Due to the dense structure and chemical stability of MgF2 film, the fluoride ion corrosion resistance of the electrode plate is improved. The surface of the electrode plate of the disclosure includes a MgF2 film capable of being used as a protective layer to protect the MgAl alloy material layer. Therefore, the electrode plate has excellent corrosion resistance against fluoride ions and can improve the quality of film formation by chemical vapor deposition.