The invention discloses an additive for improving quality of cut stem, as well as a preparation method, device and application thereof. The method comprises the following steps of: crushing dry tea flower to 20 meshes, putting into a subcritical extraction device, adding water, controlling the material-liquid ratio to be 20-40ml / g, controlling the extraction temperature at 100-120 DEG C, controlling the extraction pressure to be 7-15Mpa, extracting, then adding NaCl into an extraction solution, fully stirring and dissolving, adding CH2Cl2 into the extraction solution according to the proportion of 1: 1, fully mixing, standing for stratification, separating liquid, collecting a CH2Cl2 layer, adding anhydrous sodium sulfate, filtering, collecting filtrate, and concentrating to prepare essential oil of the tea flower, which is used as the additive for improving the quality of the cut stem. The essential oil of the tea flower according to the invention has the advantages of high extraction rate, low energy consumption, clean process, simple process and great industrial application prospects. In addition, by adding the essential oil of the tea flower, which is obtained by the preparation method, into the cut stem, miscellaneous gas of the cut stem can be effectively covered, dry tingling of smoke gas can be reduced, smoke flavor is coordinated, and the comprehensive quality of the cut stem is obviously improved.