According to closedloop communication system design of implantable devices and the communication problems, a data communication model based on volume conduction is proposed; volume conduction channel’s basic characteristic is analyzed, namely, when working frequency of volume conduction channel runs in kHz grade, biological background signal interference is insignificant. volume conduction channel can be approximated as additive white gaussian noise channel (AWGN); derived under twodimensional modulation channel capacity formula. Thus, twolevel modulation of channel capacity could be effective at very low signal to noise ratio (SNR), while multilevel modulation should be used at high SNR. Finally, using SystemView of channel simulation, the results show that the twolevel modulation is better than multilevel modulation and verify the effectiveness of the proposed method.