Abstract: Bluetooth has two defects in its security. When the encryption key is exchanged between two units, the third party can capture the encryption key as one of the two units to communicate with the other. The third party can obtain the public Bluetooth address, easily trace all operation of the unit and know the other. A new scheme was proposed to improve a link key. By making use of DES algorithm, a link key was created by constructing a Hash function to ensure both information security and establish a more robust security mechanism for the Bluetooth wireless ad-hoc network. The scheme can be regarded as a reference of revising the unit key.