This paper advances a very effective new method to solve the population balance equation (PBE) in which size growth, coalescence, breakage, and other phenomena of particles (such as nucleation) can be included. The calculation is divided into several sub-steps based on the principle of operator splitting. A growth step, a coalescence step, and a breakage step etc. are performed within one time step for a batch reactor or one space step for a column reactor. The discretization equations of the PBE are extremely simple and a stable calculation can always be obtained with this method. A sample calculation for a liquid/gas-liquid dispersion is provided.