The invention relates to a method and system for compressing and conveying a single-cycle mixed refrigerant. The method comprises the following steps of performing compressor first-section compression and cooling on the mixed refrigerant; then, entering a second section and a third section for continuous compression; then, cooling the mixed refrigerant in two steps, and forming a gas phase and a liquid phase in last-step cooling; and finally delivering into an ice chest system by differential pressure. The phenomenon that mixed refrigerant condensate generated among the sections of the compressor is avoided by the method. Based on the principle, the invention also provides the system for compressing and conveying the single-cycle mixed refrigerant. The system comprises a mixed refrigerant compressor inlet buffer tank 1, a mixed refrigerant compressor 2, a mixed refrigerant compressor first-section outlet cooler 4, a mixed refrigerant compressor second-section inlet buffer tank 3, a mixed refrigerant compressor third-section outlet cooler 5, a mixed refrigerant compressor outlet cooler 7, and an ice chest inlet separating tank 6. Compared with the traditional process, two refrigerant pumps, one cooler and one buffer tank are saved by the method and system for compressing and conveying the single-cycle mixed refrigerant. The method and the system have the advantages that the technique is simple and convenient, the investment is saved, and the operation is easy.