Since L. Datta and B. Dass proposed a spinelectronic analog of the electro-optic light modulator. This opens the way to a new field in magnetism, spintronics. The ferromagnetic material/semiconductor is a representative system in spintronics and the growth of ferromagnetic films on semiconductors offers the opportunity for many new technological applications such as magnetic tunnel junction and spin valve transistor etc.In this study, we report the experimental observation of Co growth morphology on InP (2x4) reconstruction surface. Experiments are mainly divided into two processes. First, we make a flat InP (2x4) reconstruction surface. Second, we observe the growth morphology of Co on InP (2x4) reconstruction surface by in-situ STM measurementsIn order to make InP reconstruction surface, we use IBA(Ion bombardment and annealing) method. We can obtain InP (2x4) reconstruction surface by sputterig the sample at the pressure of 2x10-7 Torr for 5 minutes, and anneling at 400°C for 30 minutes over 10 times repeatedly. We confirmed these results by RHEED and STM measurements.As the next stage, we grow Co films on InP (2x4) reconstruction surface at room temperature and below 1x10-10 Torr. We can observe four distinguishable regions with different growth morphology. At first region I (0 ML ~ 1 ML), Co deposits on row of InP (2x4) surface and grows along row direction ( ). At second region II (1 ML ~ 6 ML), the size of Co island becomes larger than that of 1 ML Co island. At third region III ( 6 ML ~ 13 ML), the roughness of Co island increases abruptly and forth region IV ( 13 ML ~ ), Co growth morphology changes from island growth to continuous film growth.