The invention relates to the technical field of microphones, in particular to an online trimmed MEMS microphone. The online trimmed MEMS microphone comprises an acoustic transducer for receiving an external ultrasonic signal and converting the ultrasonic signal into an electric signal; an ASIC (Application Specific Integrated Circuit) chip, coupled to the acoustic transducer, wherein the ASIC chip comprises: an amplifier unit for performing amplification on the electric signal and outputting an amplified signal; a decoding unit, connected to the amplifier unit, and configured to decode the amplified signal to obtain a decoded signal sequence; a matching unit, connected to the decoding unit, and configured to match the decoded signal sequence with a predetermined identification code to obtain a matched signal; a control unit, connected to the matching unit, and configured to generate one or more circuit adjusting parameters under the action of the matched signal.