A simultaneous information and energy transfer method and system with a guard interval signal are provided. The method comprises the steps of generating, by a transmitting terminal, a controllable guard interval signal according to the current energy demand and environment conditions for channel transmission. The system comprises a transmitting terminal configured to generate a controllable guard interval signal. In the system and method, the guard interval time is fully utilized to transfer a guard interval signal with controllable amount of energy, which not only prevents intersymbol interference, but also provides controllable energy signals within the guard interval time at the same time, thus improving the energy transfer performance of the system and reducing the probability that the receiving terminal is unable to operate normally due to energy shortage. The present invention can be widely applied to a variety of simultaneous wireless information and energy transfer systems.