Abstract: The structure of materials plays a crucial role in determining their performance. The performance of graphene is not only controlled by the number of layers, but also by the shape of graphene islands, which is an important factor affecting its performance. In this work, Low pressure chemical vapor deposition technology was used to grow graphene islands on the surface of liquid copper. Then, by adjusting the ratio of hydrogen and argon, controllable preparation of graphene single crystal domains with various shapes was ultimately achieved. The research results indicate that the growth rate of hexagonal graphene single crystals is much lower than that of other shapes of graphene. Based on this phenomenon, a theoretical model was proposed that covers the growth mechanism of graphene islands with different shapes. This model not only helps to understand the basic principle of graphene growth, but also will further guide the future experimental design and the development of graphene materials.