The invention discloses a lead residue reducing agent and a preparation method thereof and belongs to the technical field of chemical industry. The lead residue reducing agent comprises the following components in percentage by weight: 30 to 70 percent of active carbon, 5 to 20 percent of sodium sulfate, 5 to 15 percent of sodium hypophosphite, 1 to 15 percent of sodium hexafluoroaluminate, 3 to 18 percent of calcium oxide, 7 to 20 percent of precipitated silica, 1 to 5 percent of aluminium oxide, 1 to 5 percent of magnesium chloride, 0.1 to 2 percent of titanium trichloride and 0.5 to 5 percent of triethyl aluminum. The lead residue reducing agent can directly reduce oxide-state scum produced during alloy preparation of lead, calcium, tin and aluminum alloys and casting of grids of storage batteries into metal-state residue, so the residue amount of the lead, calcium, tin and aluminum alloys is reduced obviously. When the agent is used, the lead residue produced during the preparation of the lead, calcium, tin and aluminum alloys and the casting of grids can be directly reduced into molten metals of lead, calcium, tin and aluminum to flow back to an alloy pot, so the lead residueis reduced while the lead, calcium, tin and aluminum in the designated alloys are hardly lost; and thus, the effective ingredients of the grid alloys of the storage batteries are ensured.