The invention discloses a plant source antifertility agent for preventing and controlling grassland rats as well as a preparation method and an application thereof. The plant source antifertility agent consists of the following ingredients in parts by weight: 1-4 parts of cortex albiziae total saponins, 93-97 parts of grass meal particles and 1-3 parts of auxiliary materials. The preparation method is simple and reliable; the prepared granules have good palatability, are easy in quality standard setting, have an obvious antifertility function on male and female rats and are a novel plant source bisexual antifertility agent for preventing and controlling grassland rats.