Currently, the power supply of wireless capsule endoscopy (WCE) is poor, which limits the detection performance for gastrointestinal disease focus. A hollow 3D receiving coil is proposed, in which other modules of the WCE could be placed and the volume of the WCE is reduced further. A single turn analysis method is proposed according to the electromagnetic field theory. The induced electromotive force (EMF) and receiving power of the coil are analyzed. The uniformity performance index is proposed and the optimization model is established. The optimal design parameters of the coil is obtained. An angle attitude rotation platform was built to measure the EMF of the coil. The tested error between the measured EMF and its theoretical value is less than 6%, which verifies the rationality of the single turn analysis method and the coil design. The WCE power supplied with the designed coil was implanted into the intestine of a pig in vivo. The obtained image transmission rate is stably at 30 f/s with resolution of 400*400. The novel coil can provide sufficient and stable power, which is used for the WCE to implement gastrointestinal disease detection. The single turn analysis method can not only be applied to the designed coil, but also be applied to the power analysis of other implantable medical devices with altering relative position and angle between transmitter and receiver. The proposed method can also be used to solve the electromagnetic parameters, such as mutual inductance between transmitting and receiving coils.