In order to ensure the stable and reliable work of gastrointestinal (GI) micro-robots in human body, with the goal of expanding the working range of the wireless power transfer (WPT) system, improving the received power and its stability, studies a new type of combined solenoid WPT system. Through finite element simulation analysis, the best configuration and structure parameters of the power transmitting coil ( PTC) is determined. According to the minimum power transmitting requirement and the proposed performance evaluation index of the PTC, the number of turns of the PTC is optimized and determined. The size of the fabricated PTC is 50 cm× 50 cm×42 cm, which is 17 cm larger than that of the traditional Helmholtz coil in the axial direction, the PTC can cover the human GI region more completely. The experiment results show that using a three-dimensional orthogonal power receiving coil with a side length of 12 mm, the load received power exceeds 660 mW at any positiosn and orientations inside the PTC. In the non-edge area of the PTC, the position stability of the received power exceeds 80% . The system can meet the practical requirement of power supply for gastrointestinal micro robot.