This paper presents a sub-0.3V CMOS full-wave rectifier for energy harvesting devices. By adopting a body-input comparator with simple bias circuit, combining with body bias technique, the lowest input voltage amplitude can be reduced to 0.28V when using a standard CMOS 0.18µm process. Moreover, the voltage drop of negative voltage converter can be reduced to enhance the output voltage efficiency by adopting the proposed body bias technique. In combination with minimum reverse current and simple bias circuit in the proposed comparator, the proposed active rectifier can achieve the peak voltage conversion efficiency of over 96% and the maximum power efficiency of approximately 94%.