This paper presents a novel constant on-time (COT) single-stage reconfigurable regulating rectifier for wireless power transfer system. Compared with the discrete multi-cycle pulse-width modulation technique adopting in the previous regulating rectifiers, the proposed rectifier achieves high regulating resolution by adjusting the duty ratio continuously and smoothly. In addition, the load-transient response is much faster with the COT control method. In order to optimize the output voltage ripples, the regulating cycle is designed to be small via minimizing the on-time. Simulation results show that the maximum output power is 850mW with a peak efficiency of 93.2%.