The invention relates to a sea water desalting device, especially an internal thread flange nickel-base coupling insulation sea water desalting device without consumption power or oil to solve emergency or daily drinking water problems of an island or an anchored ship. The sea water desalting device comprises a filtering sucking pipe, a water lifting device, a pretreatment device, a high-pressure pump, a speed increaser, an abrasion-resistant alloy coupling, an entertainment actuator, a reverse osmosis membrane component and an activated carbon adsorption tank. The upper end of the filtering sucking pipe is connected with the water lifting device; a water discharge end of the water lifting device is connected with a pretreatment device; a water discharge end of the pretreatment device is connected with a high-pressure pump water intake pipe of the high-pressure pump; a high-pressure water discharge pipe is connected with an osmosis membrane inlet of the reverse osmosis membrane component; an osmosis membrane outlet is connected with an inlet of the activated carbon adsorption tank; a driving shaft of the high-pressure pump is connected with an output end of the speed increaser; an input end of the speed increaser is connected with a flange joint of the abrasion-resistant alloy coupling; the internal threaded joint of the abrasion-resistant alloy coupling is connected with an actuating output shaft of the entertainment actuator; and the entertainment actuator is provided with rotary handles.