Abstract: Theoretical analysis of crystal size distribution was made for size dependent or dispersed crystal growth under the assumption of perfect mixing and neglecting secondary processes such as agglomeration，breakage and ageing.Several relations between population density,crystallization time and crystal size for the batch solution crystallization process were obtained with the method of separating variables based on the population balance equation.These relations could be used to select the mechanism of crystal growth and calculate the linear crystal growth rate，predict the crystal size distribution and optimize the crystallization process，and regress the crystal size distribution.The results showed that this method could be used in solution crystallization process.