A control module co-constructed with a car audio apparatus has a Bluetooth module, a car audio apparatus, a sound switch and a sound control circuit. The sound switch is disposed inside the car audio apparatus and connected with the sound signal processor. It is used to choose a sound signal sent from the Bluetooth earphone or the car audio apparatus and output the sound signal via the speaker. The sound control circuit is disposed inside the car audio apparatus and connected with the sound switch. When the Bluetooth earphone is plugged into the socket of the car audio apparatus, the sound switch will silence the car audio apparatus automatically and output the sound signal sent from the Bluetooth earphone via the speaker. When the Bluetooth earphone is taken out from the socket, the car audio apparatus will serve as a common audio apparatus.