The invention discloses a mechanized crop rotation method for corn and soybeans in a northeast ridge planting region. According to the method, the corn is planted in the first year, the soybeans are planted in the second year, the corn is planted in the third year, and accordingly crop rotation is carried in a reciprocated mode; in the first planting year, the operation mode that straw smashing and returning to a field in a covering mode, stubble and smashing for turning and burying are fused is adopted, while the air speed of a soil surface is reduced, water and soil loss is reduced due to stubble operation, the amount of the straw returned to the field is kept by 30%, 30% of straw can be used for secondary smashing and returning to the field after the soybeans are harvested in the second year, in this way, 30% of straw for covering by weight still exists before seeds are sown in the third year in spring, and only 30% of straw needs to be returned to the field by weight in the third planting year; deep scarification operation is carried out at a time every three years; surface tillage operation is adopted in spring every year, surface tillage and trench bottom heavy pressing are combined to be operated. By the adoption of the new tillage and sowing combined mode and the new mode that the straw is returned to the field, rotation sowing operation is carried out on the corn and the soybeans so that melting of a frozen layer can be accelerated, soil temperature can be increased, water and soil loss can be reduced, the content of organic matter in soil can be increased, and water storage for soil moisture preservation can be achieved.