The invention discloses a liquid ammonia quality flow detection device. The liquid ammonia quality flow detection device comprises a liquid ammonia gas-liquid separator, a pipeline liquid-level container, a liquid-level transmitter, an adjustment valve and a quality flowmeter, wherein a liquid ammonia inlet main pipe line and a gas ammonia outlet main pipe line are respectively connected with theliquid ammonia gas-liquid separator; the liquid ammonia gas-liquid separator is connected with the pipeline liquid-level container; the liquid-level transmitter is mounted on the pipeline liquid-levelcontainer; a lower pressure tapping hole of the pipeline liquid-level container is connected with a positive pressure side of the liquid-level transmitter; an upper pressure tapping hole of the pipeline liquid-level container is connected with a negative pressure side of the liquid-level transmitter; the lower part of the pipeline liquid-level container is sequentially connected with the qualityflowmeter and the adjustment valve. According to the liquid ammonia quality flow detection device, the density and quality of liquid ammonia is directly measured by the quality flowmeter, so that thedifficulty that measurement of gas blow-by is inaccurate by adopting the liquid ammonia quality flowmeter is solved through the control of the two stage separation of the liquid ammonia gas-liquid separator and the pipeline liquid-level container. The liquid ammonia quality flow detection device disclosed by the invention has the advantages of high security, more stability and reliability, low cost, convenience in operation and simpleness in control, and moreover, the difficulty that measurement of gas blow-by is inaccurate by adopting the liquid ammonia quality flowmeter is solved.