Diffusion-limited aggregation (DLA) model has been widely used to simulate the aggregation processes. In this work, the aggregation of wax and asphaltene particles in crude oil is studied with a modified DLA model. Assuming both wax and asphaltene particles are sphere, the co-precipitating process could be regarded as a simple aggregation process containing two kinds of particles. Three important parameters are discussed, as the sticking coefficient between particles, the ratio of particle size, and the particle concentration. Via analyzing the fractal dimension of the formed aggregates, the aggregation mechanism of wax and asphaltene particles could be explained, and help to further reveal the nature of the disordered growth. (C) 2016 Elsevier Ltd. All rights reserved.