The growth of self-assembled nanowires on stepped substrates is modeled by means of kinetic Monte Carlo simulations. It is found that the energy barrier at the step edges has a great effect on the formation of nanoislands on stepped substrates. As the barrier is smaller than 0.1 eV, nanowires with high aspect ratios can be obtained. The width, aspect ratio, and separation of the nanowires can be controlled flexibly by the width of the steps or terraces of the substrates. The effects of growth temperature and postgrowth annealing time on the morphology of the nanowires are studied. The nanowires are found to be more robust than the self-assembled nanoislands formed on plane substrates. Strain is shown to increase the width and decrease the aspect ratio of the nanowires. The scaled nanowire length distribution is also studied. As the coverage is larger than 0.2 ML, the distribution is apparently different from that at lower coverage, which reflects the different growth mechanisms of the nanowires at different layer thickness.