The invention provides a nuclear power station underwater foreign matter suction apparatus. The apparatus comprises a water pump with a motor, a water inlet pipe, a water outlet pipe and a filter barrel connected with the inlet of the water pump and placed over the water pump, the filter barrel comprises a shell, a barrel-shaped filter screen placed in the shell and a top cover hinged to the shell and used for sealing the top of the shell, one end of the water inlet pipe stretches into the filter barrel, the other end of the water inlet pipe is connected with a foreign matter suction pipe, and the water outlet pipe is connected with the outlet of the water pump. The water pump is adopted to form a negative pressure in the filter barrel, so water in a reactor pool goes through the water inlet pipe, enters the filter barrel and is filtered, foreign matters enter the filter barrel with water flow, and above processes are repeated in order to suck the foreign matters in water. The suction apparatus has the advantages of simple structure, small size, easy placement in water by an operator, easy operation, realization of the rapid catching of the foreign matters in water without accurate positioning, and time saving.