A micro-electro-mechanical-system (MEMS) device comprising two proof masses disposed in the first frame, such that the MEMS device with oscillating assemblies senses the angular velocity in the two axes, respectively. The MEMS device with oscillating assemblies further comprises a lever structure and two oscillating assemblies connecting at two opposite ends of the lever structure, such that the oscillating assemblies move in opposite directions synchronously. The MEMS device with oscillating assemblies further comprises a spring assembly connected between the proof mass and a movable electrode, restricting the proof mass to drive the movable electrode to only move in a specific direction.