The invention relates to the technical field of compound extracting, in particular to a method for extracting urea from ornithine-aspartate crystallization mother liquid. The method includes the following steps that the ornithine-aspartate crystallization mother liquid synthesized by immobilized enzyme is filtered, and filtered liquid is obtained; the filtered liquid is subjected to atmospheric distillation, and atmospheric concentrated liquid is obtained; the atmospheric concentrated liquid is subjected to pressure reduction concentration, and pressure reduction concentrated liquid is obtained; the pressure reduction concentrated liquid is subjected to spray granulation, and after drying treatment is carried out, urea fertilizer is obtained. According to the method for extracting the ureafrom the ornithine-aspartate crystallization mother liquid, the technology is simple, operation is easy and convenient, a product can be further recycled through filtering treatment, and the productyield is increased; a solvent can be recycled through atmospheric distillation, and is mechanically applied, and the cost is reduced; by-product urea is extracted and prepared into the fertilizer, andthe economic value is improved.