The invention discloses a manual desalination device for a life raft. The manual desalination device comprises a power mechanism used for pumping seawater, a desalination mechanism connected with the power mechanism and a drinking water storage tank. The manual desalination device is characterized in that the power mechanism comprises a reciprocating pump provided with a suction pipe and a discharge pipe, wherein the suction opening of the suction pipe is inserted in seawater, the discharge pipe is connected with the water inlet of a reverse osmosis filtration membrane by virtue of a pipeline, a plunger rod is connected to a piston of the reciprocating pump, the other end of the plunger rod is rotatably connected with a connecting rod, the other end of the connecting rod is rotatably connected with a disk provided with a handle, when the disk rotates in a reciprocating manner, the connecting rod performs rectilinear motion under the action of a guide sleeve so as to drive the plunger rod and the piston to perform rectilinear reciprocating motion to discharge and feed liquid in the reciprocating pump. Since a manual operation is adopted, the manual desalination device can be randomly used without being limited by yields and has the advantages of convenience for use, small volume size and light weight; by adopting the manual desalination device, no special drinking water is allocated on a lifeboat or the life raft, so that the cost is saved, furthermore, the manual desalination device can be randomly used and is environmental-friendly and energy-saving. While desalinating water, the manual desalination device disclosed by the invention can be used for removing harmful substances and increasing mineral substances necessary for a human body, so that the seawater can be directly drunk after being treated and the manual desalination device is safe and sanitary.