The deposition, diffusion and coalescence processes appeared in the surface growth of compact or liquid-like clusters system are studied. By introducing a critical cluster size ic, such that clusters of size s≤ic are mobile while clusters of the size s ＞ ic are immobile, the effects of mobility of small clusters on cluster size distribution are simulated. As ic increases, the exponent γ which relates the maximum cluster density to the normalized deposition rate is increased. Numerical simudation results indicate that the scaled cluster-size distributions are independent of the deposition rate, but closely associated with the small clusters mobility. As ic increases, it is found that the distributions become narrow.