The invention discloses a method for returning crop stalks to a field. The method comprises the following steps of S1, digging a sunken composting pool in a crop harvesting season; S2, smashing the harvested crop stalks, pouring the smashed crop stalks into the sunken composting pool, spreading the crop stalks until the thickness is 0.8 m-1m, covering the crop stalks with a layer of field soil with the thickness of 5 cm, compacting, and watering until the crop stalk powder and the field soil are wet to obtain a pretreated fertilizer pile; S3, covering the surface of the pretreated fertilizer pile with 1 layer-2 layers of agricultural mulching films, and standing to enable the crop stalk powder to be subjected to water-logged composting in the sunken composting pool until the crop stalk powder becomes a decomposed fertilizer; S4, when the next harvesting season begins, removing the agricultural mulching films, directly taking the decomposed fertilizer, and uniformly scattering the decomposed fertilizer into the field after the crops are harvested and before ploughing; and S5, repeating the steps S2-S4. According to the method for returning the crop stalks to the field, the harm to soil and crops caused by traditional direct crop stalk returning is avoided, waste gas and waste water generated during water-logged compost can be prevented from leaking to pollute the environment, the quality of the soil and the crops can be improved, the implementation is simple, and continuous circulation can be realized.