The invention belongs to the field of ant-killing agents, and particularly provides a plant-sourced ant-killing bait and a preparation method thereof. The plant-sourced ant-killing bait comprises an ant-killing agent and a filling bait, wherein the ant-killing agent comprises a laurel essential oil, fructus cnidii essential oil, macleaya cordata total alkaloid and rotenone; the filling bait comprises flour, corn flour, butter, peanut oil and diatomite. The preparation method comprises the following steps: mixing the diatomite, the butter and the peanut oil, adding the corn flour and water, blending into a paste, adding the flour and water, making dough, and baking till a crispy state; dissolving the laurel essential oil, the fructus cnidii essential oil, the macleaya cordata total alkaloidand the rotenone into an acetone-water solution system to obtain the ant-killing agent, soaking the filling bait by using the ant-killing agent, drying in a drying box, crushing, and sieving by usinga 10-18-mesh sieve. The plant-sourced ant-killing bait is prepared from plant-sourced bioactive substances, has low active component toxicity, has a low acting effect, easily avoids ant colony diffusion, and has a high-efficiency and complete ant-killing effect during red imported fire ant control.