The invention discloses a method for synthesizing a farmland rodenticide. The rodenticide comprises 7-12 parts of diisocyanate, 5-15 parts of tripterygium wilfordii, 5-10 parts of animal and vegetable oil, and 10-20 parts of corn flour in parts by weight. , 1‑4 parts of essence, 10‑20 parts of sodium alginate, 7‑15 parts of tetramethrin, 2‑6 parts of bentonite, 5‑10 parts of ricinine, 1‑3 parts of maduramycin, indomethacin 3‑6 parts, 10‑20 parts of diclofenac sodium, 2‑6 parts of 4‑hydroxycoumarin, 10‑20 parts of bone grass powder, 10‑15 parts of fulvic acid and 3‑8 parts of citric acid, The preparation process of the invention is simple, and the prepared rodenticide can effectively kill voles, and the long-term use will not cause harm to crops and soil, and has the effect of non-toxicity and environmental protection.