This invention provides a signal processing method of multiple micro-electro-mechanical system devices. The signal processing method includes: providing at least two MEMS devices; applying driving or modulating signals of different frequencies to the MEMS devices such that the MEMS devices generate respective MEMS signals with respective frequencies; and combining the MEMS signals with respective frequencies into one or more multi-frequency signals and outputting the multi-frequency signals, wherein a number of the multi-frequency signals is less than a number of the MEMS signals with respective frequencies. This invention also provides a combo MEMS device integrating two or more MEMS devices and two or more vibration sources.