GeSn is an important Si based semiconductor material due to its direct band characteristic. The small amount of Sn into GeSn alloy will induce a high-efficiency optical detection in the full-band communication at low concentration of Sn (approximately 3%). It has attracted lots of attention in recent years. However, due to the low solid solubility of Sn in Ge and large lattice mismatch, the growth of GeSn on Si is still a challenge. High-quality GeSn alloy have been grown by molecular beam epitaxy (MBE) and chemical vapor deposition (CVD), but there is still high the dislocation density. We have reported a new way to grow the defect-free GeSn alloy strips on Si substrates with the assistance of Sn. The lateral growth of GeSn alloy strips were grown on Si(111) by Sn self-catalyzed method. The GeSn materials are grown in a custom-designed MBE system with a base pressure of 5 × 10⁻⁸ Pa. The Here the growth of GeSn strips are studied on pattered substrate. We will discuss the growth mechanism and the impact factors on the materials. It is found that Sn has an important impact on morphology of the GeSn materials and different depositions and annealing times of Sn will impact the morphology of the materials. GeSn alloy strips show a good quality by the TEM micrographs and the SAED patterns(Fig.1). No dislocation is found in the grown material. GeSn growth on patterned substrate is also discussed.