The present invention discloses a vibration diaphragm in an MEMS microphone, and an MEMS microphone. The vibration diaphragm comprises a vibration diaphragm body and at least one pressure relief device defined by gaps in the vibration diaphragm body, wherein the gaps comprise at least two sections of circular arc-shaped gaps sequentially connected together. The two adjacent sections of circular arc-shaped gaps are in an S shape as a whole and centrosymmetrical with respect to a connected position thereof. The pressure relief device comprises at least two valve clacks formed by at least two sections of adjacent circular arc-shaped gaps and neck portions connected to the valve clacks and the vibration diaphragm body and of a constraint shape.