A communication system of an implantable device, comprising an external unit and an implantable unit, and wherein the external unit and the implantable unit realize charging and bidirectional signal transmission of the external unit to the implantable unit by a wireless signal, wherein the external unit comprises a digital signal processing unit, a power transmission unit and a receiver and demodulation unit, the implantable unit comprises a stimulation module and a signal receiver and transmission unit, the power transmission unit of the external unit comprises a first coupling coil L1, the first coupling coil L1 is configured to transmit a signal to the implantable unit, the signal receiver unit of the implantable unit comprises a second coupling coil L2, the second coupling coil L2 is configured to receive the signal from the external unit and transmit a signal to the external unit, the receiver and modulation unit of the external device comprises a third coupling coil L3, and the third coupling coil L3 is configured to receive the signal from the implantable unit, characterized in that, the third coupling coil L3 comprises two symmetrical parts, the coils on the two symmetrical parts are arranged to cross each other through a symmetric center, a cross point thereof overlaps with a center of the first coupling coil L1, there is an offset between a center of the second coupling coil L2 and a center cross point position of the third coupling coil L3, and a positive and negative current generated by coupling the first coupling coil L1 through the third coupling coil L3 cancel each other out, and a size of the first coupling coil L1 is larger than a size of the second coupling coil L2, the second coupling coil L2 is in the projections of the first coupling coil L1 and the third coupling coil L3. wherein the external unit comprises a digital signal processing unit, a power transmission unit and a receiver and demodulation unit, the implantable unit comprises a stimulation module and a signal receiver and transmission unit, the power transmission unit of the external unit comprises a first coupling coil L1, the first coupling coil L1 is configured to transmit a signal to the implantable unit, the signal receiver unit of the implantable unit comprises a second coupling coil L2, the second coupling coil L2 is configured to receive the signal from the external unit and transmit a signal to the external unit, the receiver and modulation unit of the external device comprises a third coupling coil L3, and the third coupling coil L3 is configured to receive the signal from the implantable unit, characterized in that, the third coupling coil L3 comprises two symmetrical parts, the coils on the two symmetrical parts are arranged to cross each other through a symmetric center, a cross point thereof overlaps with a center of the first coupling coil L1, there is an offset between a center of the second coupling coil L2 and a center cross point position of the third coupling coil L3, and a positive and negative current generated by coupling the first coupling coil L1 through the third coupling coil L3 cancel each other out, and a size of the first coupling coil L1 is larger than a size of the second coupling coil L2, the second coupling coil L2 is in the projections of the first coupling coil L1 and the third coupling coil L3.