The invention relates to a method for recovering solid slag slurry obtained by carrying out cold hydrogenation on polycrystalline silicon. According to the method, the solid slag slurry is firstly dried and concentrated in a closed environment, a generated gas passes through a defoamer and then is emitted, the concentrated solid slag slurry is secondly dried through a spiral feed pump and then delivered into a dynamic filter press to be simultaneously hydrolyzed and filtered, a hydrolyzate is separated in time, so that the hydrolysis efficiency is increased, and the pollution of a toxic gas on the environment is prevented because the integral process is carried out in the closed environment; a closed type drying machine is adopted, and the defoamer is arranged on a gas outlet position, so that the dust is prevented from entering a post-processing process; the re-slurrying hydrolysis reaction, washing and thickening dehydration of the solid slag slurry are carried out in the dynamic filter press, the filtration is carried out at the same time, so that the reaction efficiency is increased, the usage amount of alkali liquor and the discharge amount of waste water are reduced, and the hydrolysis efficiency is increased.