The invention discloses a system for increasing the yield of liquid argon. The system comprises a first crude argon column, a second crude argon column, a buffer tank and a pure argon column. The first crude argon column is connected with the second crude argon column; the second crude argon column is connected with the buffer tank; and the buffer tank is connected with the pure argon column. The first crude argon column performs oxygen and argon separation on argon fractions with the oxygen content ranging from 88% to 92%, which are extracted in the middle of an upper column of an air separation system, and transmits crude argon with the oxygen content smaller than 3%, which is obtained after separation, to the second crude argon column. The second crude argon column performs oxygen and argon separation on the received crude argon with the oxygen content smaller than 3% again and outputs argon obtained after separation, of which the oxygen content is smaller than 3ppm, to the buffer tank. The buffer tank stores the received argon with the oxygen content smaller than 3ppm and outputs the argon to the pure argon column after the flow and the pressure are balanced. The pure argon column performs oxygen and argon separation on the received crude argon with the oxygen content smaller than 3%, which is output by the buffer tank, to extract pure liquid argon products. By means of the system, the yield of liquid argon can be improved.