The invention discloses an early sowing method for the rice field milk vetch. The early sowing method for the rice field milk vetch comprises the following steps: a) sowing the milk vetch: in the late rice tillering last stage to the full heading time, sowing the milk vetch with the sowing amount of 2.0-2.5kg per unit of area when the field water content is less than 15%; b) managing field water: after sowing, keeping the field water content at 10-40%, opening a ridge ditch hole to discharge water after the milk-ripe stage of the late rice, ensuring that the field is under the drying state when the rice is harvested, then, harvesting the late rice by the harvester, regulating distance between the header of the harvester and the ground to be 45-55cm when the late rice is harvested, and evenly spreading the accumulated straw in the field after the rice is harvested; and c) ditching a land for growing field crops: after the late rice is harvested, digging a surrounding ditch around the field by a ditcher to ensure that the highest water level of the field does not exceed 0.5cm. The early sowing method for the rice field milk vetch, which is disclosed by the invention, is combined with the necessary farm operation of the rice in the rice growth period when the rice field operation is convenient, and water management is reasonably carried out to simplify the milk vetch sowing.