Hydrocyclones are widely used in both mining and various industrial sectors. Considerable fundamental research work on the modelling of hydrocyclone classifiers has been carried out through the past 25 years. Based on the similarity principle, the hydrocyclone classification was taken as a whole physical process and a group of similarity numbers were obtained with the help of dimensional analysis in this paper. Then, the functional dependences of the similarity numbers have been established. The variables optimisation was carried out with the multiple objectives linear planning programs developed in this study.