The invention discloses an efficient liquid exchanging method based on a vacuum gas quenching furnace. The efficient liquid changing method includes the following steps of temperature detection, temperature judgment and liquid level judgment, a liquid level sensor emits two signals c, d and e according to the detected liquid level of cooling liquid, the signal c indicates a liquid level lower thanthe normal level, d indicates a normal liquid level, and e indicates a liquid level higher than the normal level; and liquid adding pipelines are switched. The invention further discloses an efficient liquid exchanging system based on the vacuum gas quenching furnace, and the efficient liquid exchanging system comprises a temperature detection assembly, a liquid level detection assembly and a liquid exchanging assembly, wherein the liquid exchanging assembly comprises a cooling liquid tank, a new cooling liquid adding channel pipe and an old cooling liquid adding channel pipe; the temperaturedetection assembly comprises a temperature detector and a temperature sensor; and the liquid level detection assembly comprises a liquid level detector and the liquid level sensor. The efficient liquid exchanging system effectively realizes automatic liquid exchanging and controls the temperature of quenching liquid.