A power processing interface for a radio frequency identification system is provided. The power processing interface includes a resonance circuit for inducing a first signal transmitted from a terminal as an AC voltage, a first rectifier circuit electrically connected to the resonance circuit for converting the AC voltage into a DC voltage, a filter circuit electrically connected to the first rectifier circuit for generating an operating voltage in response to the DC voltage, a voltage-detecting circuit electrically connected to the filter circuit and the first rectifier circuit for detecting the magnitude of the operating voltage, a second rectifier circuit electrically connected to the resonance circuit, and a voltage-clamping modulation circuit electrically connected to the first rectifier circuit, the voltage-detecting circuit and the second rectifier circuit for controlling the conduction of the second rectifier circuit in response to the output of the voltage-detecting circuit so as to bypass the excessive current, and for providing a minimum voltage to the radio frequency identification system during the modulation process so as to keep the radio frequency identification system in a normal operation.