A mathematical model is derived describing the steady state operation of a continuous cooling-type crystallizer. The system considered for testing the model is magnesium sulfate heptahydrate-water. Nucleation and growth rate expressions for the system are derived from experimental data obtained from the literature. A computer program was developed so as to facilitate solution of the non-linear system equations. The model was tested with various sets of hypothetical input data so as to determine crystallizer and heat exchanger design parameters given the data describing the desired steady state operation, and to determine the effect of changes in steady state operating conditions on crystallizer output （particle size distribution and yield）. The techniques developed in this study provide a means to the solution of pertinent engineering problems associated with this type of crystallization process.