The invention discloses a method for developing natural gas hydrate, which comprises that building developing well, horizontal well and collecting well, building floating platform and natural gas hydrate developer on sea, building sea concentration heater, preparing hot salt water, decomposing natural gas hydrate and collecting natural gas. And the inventive device comprises a sea floating platform, a developing well, a collecting well, a horizontal well, a hydrate recycling system, a fresh water groove, a hot salt water tube, a hot salt water pump, and a seawater concentrating heater. The invention has simple process, low energy consumption and low cost, without pollution.