A population balance model was developed to determine the evolution of crude oil asphaltene aggregate size distribution. The model predictions have good accuracy in comparison with experimental results that were obtained by the image processing method. The fractal nature of asphaltene aggregates was attended assuming fractal dimension equal 1.6. Effects of shear rate, solvent composition, and initial particle size were studied on the evolution of number average diameter. The average diameter of particles reaches a maximum value and then declines to a steady state size. Shear rate and initial average diameter affect the maximum diameter and its time, but initial size has no effect on the steady state size. The combination of the image processing method and fractal approach determines the asphaltene solid content of samples. Asphaltene was extracted from Iranian heavy crude petroleum using toluene and normal heptane.