The effects of the solvent-surfactant interaction, chain length and stiffness of surfactants on the formation of aggregates and the aggregation degree of surfactants in the two-dimension solution have been investigated using discontinuous molecular-dynamics simulations. When the tail-water repulsion increases or the head-water attraction decreases, the aggregation degree increases. Increasing the chain length and raising the stiffness of surfactants lead to the increment of the aggregation degree.