The invention relates to a system and method for utilizing waste heat of inner ring water of a gas turbine. An existing system for utilizing waste heat of inner ring water of a gas turbine difficultly utilizes low-quality heat fully. The system comprises the gas turbine, and is characterized by further comprising a waste heat boiler, a heat exchanger, a softened water treatment device and a steam heat exchanger, wherein a smoke outlet of the gas turbine is connected with a smoke inlet of the waste heat boiler by a smoke waste heat utilizing pipe; a high-temperature water side outlet of the heat exchanger is connected with an inner ring water inlet of the gas turbine by an inner ring water reflux pipe; a low-temperature water side outlet of the heat exchanger is connected with a water inlet of the softened water treatment device by a water outlet pipe; a water outlet of the softened water treatment device is connected with a water replenishing opening of the waste heat boiler by a water replenishing pipe; an inlet of a raw water bypass stop valve is connected with a raw water pipe; and a water side outlet of the steam heat exchanger is connected with a water inlet of the softened water treatment device by a bypass water outlet pipe. By the system and method for utilizing the waste heat of the inner ring water of the gas turbine, the low-quality heat can be utilized fully, and the economic benefit is good.