Method and system for exploiting combustible ice natural gas by using deep formation hot water

Disclosed is a method for exploiting natural gas by using deep formation hot water. The method includes the following steps: (1) exploring a hot water layer in a deep part of a formation when exploring combustible ice storage; (2) when well drilling is completed, letting a well pass through a combustible ice layer to reach the hot water layer at the lower part; (3) determining a combustible ice natural gas exploitation layer section, a hot water exploitation layer section and a pore reservoir; (4) establishing a communication channel between the three sections of the combustible ice layer, thehot water layer and the pore reservoir with a wellbore by means of perforation; (5) placing an exploitation production pipeline and a sand control device and an injection control device connected tothe bottom of the exploitation production pipeline in corresponding downhole positions; (6) exciting natural gas exploitation of the combustible ice layer by a pressure reduction method; (7) exploiting hot water in the deep fo