A protection case for a mobile communication device includes a main body for receiving the mobile communication device, a main circuit board with an amplifier installed thereon, and a vibrator electrically connected to the amplifier. The amplifier comprises audio signal input terminals for receiving audio signals from the mobile communication device, and audio signal output terminals for outputting the audio signals which are amplified by the amplifier to the vibrator; the vibrator is driven to vibrate in accordance with the audio signals output by the amplifier.