The random characteristic of particles motion and separation process were studied. A Lagrange method was introduced to detect the particle motion trajectory by height speed analyzer. More than a hundred tests were carried to evaluate the particle motion trajectory and separation characteristics. Statistical analysis of the particle motion trajectory showed that the separation process of particles has stochastic characteristics which is related with the initialization position at inlet section and diameter of a particle, as well as the cone angle of hydrocyclone. On the other hand, for single particle, the chance of particle entrance into underflow or overflow is random. For particles cluster, they had statistical property and kept the characteristic which was the probability of a big particle entering into underflow is larger than a small particle. Those above have provided the evidence for comprehensively understanding separation mechanism and reliable structure design of the hydrocyclone.
