A master-slave communication circuit includes a master device, a number of slave devices, and a bus providing communication channels between the master device and the slave devices. Each slave device includes an identification (ID) address setting unit, a plug-in detecting pin, and a plug-out detecting pin. The identification (ID) address setting unit is connected to the bus to receive an ID address setting signal transferred from the master device, and set an ID address to the corresponding slave device. The master sets the ID addresses of the slave devices according to voltage levels of the plug-in detecting pin and the plug-out detecting pin, to make the ID addresses of the slave devices connected to the bus are different.