The invention discloses a mold release agent for a battery plate grid and a preparation method thereof, and relates to the technical field of mold release agent preparation. The mold release agent isprepared from the following raw materials in parts by weight: 95 to 105 parts of pure water, 0.5 to 0.8 part of bone glue, 0.1 to 0.3 part of polyvinyl alcohol, 1.9 to 2.3 parts of cork powder, 0.1 to0.3 part of aluminum hydroxide, and 0.1 to 0.3 part of phosphoric acid. The preparation method comprises the steps of stirring the pure water, the bone glue, the polyvinyl alcohol, the aluminum hydroxide and the phosphoric acid, heating to 100 DEG C, completely dissolving, cooling for 30 minutes, heating until boiling, adding the cork powder, stirring uniformly, and cooling for standby use. According to the mold release agent for the battery plate grid and the preparation method thereof provided by the invention, through adjusting a formula of the mold release agent, adjusting the contents ofthe pure water, the bone glue, the polyvinyl alcohol, the cork powder, the aluminum hydroxide and the phosphoric acid, and preparing the mold release agent according to a technological process, the mold release agent is good in adhesiveness and long in service life; the plate grid is uniform in weight and smooth and level in surface; and the negative phenomena of rib burning, airhole generating and crack forming are effectively reduced, so that the production efficiency is improved.