A MEMS device includes: a substrate; a proof mass suspended over the substrate, the proof mass including at least one proof mass body and a proof mass frame connected to and accommodating the proof mass body, the proof mass frame including at least one self-test frame; and at least one self-test electrode inside the self-test frame, and connected to the substrate; wherein when a voltage difference is applied between the self-test electrode and the self-test frame, the proof mass is driven to have an in-plane movement, and wherein the self-test electrode and the self-test frame do not form a sensing capacitor in between.