Based on the Monte-Carlo simulation, magnetic dynamic properties of magnetic clusters and quasi two-dimensional quantum dots with hexagonal lattice arrays have been calculated. It has been found that the saturation fields for the cluster and quantum dot increase with increasing dipolar interaction. However, hysteresis loops of the quantum dots are different from those in clusters. Hysteresis behavior of quantum dot array is associated closely with the radius of quantum dot and the distance between quantum dots. The calculated results are consistent with experimental results. Finally, the step effect of hysteresis loops has been explained by the competition roles among the configurational anisotropy energy, Zeeman energy and thermal energy.