The magnetic resonant wireless power transfer system with a function of human tracking has been proposed in order to supply the electrical energy to a power assist robot suit. A simple and fast algorithm using the gradient ascent to calculate optimal coil position based on the position and attitude of a receiver coil was developed. Simulation results showed that the optimal coil positions and attitudes of the transfer and repeater coils were calculated within 0.1 s. Even the receiver coil moved with a speed of 1 m/s, the algorithm could give the coil positions within the sufficient time to keep the high transfer efficiency. The simulated optimal coil position was compared with the experimentally measured optimal position and they showed good agreement each other.