The present disclosure discloses a non-grain monogastric animal feed and a preparation method thereof, and relates to the technical field of feed processing. In particular, the non-grain monogastric animal feed includes steam-exploded Eupatorium adenophora Spreng. And Amaranthus hypochondriacus L. as main raw materials, and is prepared by thoroughly mixing 200 to 800 parts of an Eupatorium adenophora Spreng. powder, 200 to 500 parts of an Amaranthus hypochondriacus L. powder, 200 to 400 parts of a Rumex dapibus herba by. powder, 10 to 50 parts of an Acer truncatum Bunge leaf powder, and 10 to 50 parts of a premix in parts by weight. In the present disclosure, Eupatorium adenophora Spreng., Amaranthus hypochondriacus L., Rumex dapibus herba by., or the like are adopted as protein feed resources to replace all raw materials such as com and soybean meal in monogastric animal feeds, which can not only save grains, but also allow the utilization of Eupatorium adenophora Spreng. To alleviate the damage of Eupatorium adenophora Spreng. to the ecological environment to some extent and turn a harmful substance into a treasure. In addition, the present disclosure can reduce a farming cost, enhance the immunity, promote the growth, and improve a meat quality, and is conducive to the promotion and use. Therefore, the present disclosure can bring excellent economic and ecological benefits.