Abstract: The cluster-agglomeration pattern was simulated with DLA model in the fractal theory to study the agglomeration process of a great number of inclusion particles in molten steel. The results show that the shapes of agglomerates are alike to the cluster type inclusion particles in molten steel. By the rule in the fractal theory the agglomeration process can be considered as follows. Numerous inclusion particles aggregate to form smaller clusters firstly, and then they come together into large agglomerates. The agglomerating times of clusters equal in size are different, The shapes of clusters with the same initial condition of agglomeration are also different. The inclusion growth rate by agglomeration increases with increasing shift step length and concentration of particles. The average value of shift step length of particles is decided by the viscosity of molten steel and the size of particles with a great degree. The distribution of agglomerates and the size of clusters vary with the agglomerating time and the average shift step length of particles.