Intra-body Communication (IBC) is an emerging and interesting communication technique in recent years. The research and promotion of this technique is to simplify the communication network of telemedicine system, wearable device, as well as implantable devices. Utilizing the conductive property of human body, IBC employs human body as communication medium for transmitting/receiving electrical signals. As a result, abundant of interconnected cables and electromagnetic interference can significantly be reduced for telemedicine system and IBC can provide an alternative solution for realizing the communication with implantable devices. In this paper, the authors propose a quasi-static mathematical model for galvanic coupling type IBC. This model attempts to provide insight of transmitting electrical signal through human body and forms a basis for developing IBC applications. Finally, experimental measurements are conducted for validating the correctness of the model.