The precipitation is a process involving complicated crystallization and mass transfer. As a key step in the Bayer process in alumina production, it has great influences on both outputs and quality of alumina products. Thus laboratory experiments, industrial tests and numerical simulations have been carried out to study the precipitation. Based on the dynamics law and particle population balance, a combined model is developed with MATLAB/Simulink to study the process of crystal nucleation, growth and agglomeration, the model also take the variation characteristics of the particle size of the MSMPR (mixed-suspension, mixed product removal) gibbsite precipitation process into account. The particle size distribution is predicted through the method of moments at different conditions. The deviation between the model prediction and the test data is less than 9%, which is within the acceptable accuracy range for the process control. (C) 2011 Elsevier B.V. All rights reserved.