To tackle the issues of oversize and inconvenient wearing of the conventional wrap-around-style transmitting coil, a novel wireless power transfer (WPT) system for capsule robots is proposed in this paper. The key is to adopt a planar spiral coil as the transmitting coil, which effectively reduces the size of the transmitting coil, as well as avoids the inconvenient wearing issue. As a result, the capsule robot-oriented WPT system becomes more adaptive. Firstly, the equivalent circuit model is established, the relationship between system transmission efficiency and system parameters is studied. Then, the turns of the receiving coil are optimized to promote the transmission efficiency of the system. After that, the equivalent load resistance is optimized with an impedance converter. Finally, the wireless power transmitting system based on the proposed scheme is verified by several experiments. The results show that an overall transmission efficiency of prototype system 8.8% is realized at 10 cm distance with the output power larger than 1 W.