The present invention provides a method for producing a high-purity liquid hydrogen cyanide for hydrogen cyanide gas obtained by ammoxidation. The liquid hydrogen cyanide of a low water content is obtained by absorption of low-temperature water in an absorbing tower and operation of a three-stage distillation tower and a gas-liquid separator. The process and method have the beneficial effects that by virtue of adoption by low-temperature water, the absorption efficiency of HCN gas is improved, the load on subsequent exhaust gas processing facilitates is alleviated, and the environmental protection pressure is relieved. Refined by the process disclosed by the invention, the content of a finished product hydrogen cyanide water can reach below 50 ppm, thereby sufficiently satisfying the using requirements on downstream users; the leakage risk of the hydrogen cyanide is effectively avoided, thereby more facilitating the safe production; and self-polymerization of hydrogen cyanide can be further slowed, so that production is more smooth and the production efficiency is improved.