A demulsification process of phosphoric acid-tributyl phosphate emulsion by using a liquid-liquid hydrocyclone was investigated. In this study, the droplet size distributions and average droplet sizes of the emulsions pre and post demulsification were measured and were used to evaluate the demulsification performance. The effects of the inlet flow rate and the structural parameters such as large cone part angle, small cone part angle, cylindrical part height, inlet inner diameter and overflow pipe inner diameter of the hydrocyclone on the demulsification performance were investigated. The optimum inlet flow rate and structural parameters were obtained. Under the optimum conditions, average droplet size of the emulsion increased from 4.78 to 55.07 mu m, the difference was 50.29 mu m. The average droplet size differences were associated with these above-mentioned parameters through a dimensionless model. The comparison of experimental and calculated data showed that this model was reliable to predict the average droplet size difference in most demulsification conditions by hydrocyclone. (C) 2015 Elsevier B.V. All rights reserved.