The invention provides a method for manufacturing a MEMS microphone, including the steps of: providing a base and preparing a first diaphragm on a first surface of the base; preparing a back plate on a surface of the first diaphragm opposite to the first surface; forming a first gap between the first diaphragm and the back plate; preparing a second diaphragm; forming a second gap between the second diaphragm and the back plate; preparing electrodes; forming a back cavity by etching the surface opposite to the first surface.