The invention discloses a method for preparing sodium thiocyanate by using desulphurization waste liquid of coke oven gas, and belongs to the technical field of utilization of desulphurization waste liquid of the coke oven gas. The method comprises the following steps: using the desulphurization waste liquid of the coke oven gas as a raw material, firstly, filtering the waste liquid in vacuum, using tributyl phosphate to extract thiocyanate radicals in the waste liquid, then using sodium hydroxide solution to back-extract the extract, and finally concentrating and crystallizing the extract, and washing and drying the crystals to obtain sodium thiocyanate crystals. The method uses the desulphurization waste liquid of the coke oven gas to prepare a sodium thiocyanate product with the purity as high as 93 to 95 percent so as to change waste into valuable and makes full use of waste resources; and the method is simple, saves energy, has no three-waste discharge, is favorable for environmental protection, has low production cost and good economic benefit, and develops a new path for the utilization of the desulphurization waste liquid resources of the coke oven gas. The sodium thiocyanate product prepared by the method can be widely applied in the industries of medicaments, textile, printing and dyeing, pesticide, chemistry and the like.