The invention discloses a preparation method and device of lactide, belonging to the technical field of material preparation. The preparation method comprises the steps of preparing crude lactide, and preparing refined lactide from the crude lactide, wherein the step of preparing the refined lactide from the crude lactide comprises the following steps: sequentially adding a disacidifying agent and a dewatering agent into the crude lactide under a first temperature condition, so as to obtain a first intermediate product; heating the first intermediate product to a second temperature condition to melt the crude lactide to continuously react for a set time, so as to obtain a second intermediate product; and continuously heating the second intermediate product to a distillation temperature, decreasing the pressure of the second intermediate product to a set system vacuum degree, and distilling the second intermediate product, so as to obtain distillate, namely the refined lactide. The preparation method can be realized by virtue of the preparation device. The preparation method and the preparation device have the beneficial effects that the purification cost is low, the operation is convenient, the production efficiency is high, and furthermore, the yield and purity of the refined lactide are remarkably increased.