Screw dislocation driven growth in 2D materials could result in spiral structure and bring about plenty of intriguing properties such as vertical conductivity through the screw dislocation core and nonlinear optical generation, piezoelectricity and ferroelectricity through the inversion symmetry breaking by the spiral growth. However, the control of spiral growth in 2D materials is still immature because of the random occurrence of screw dislocation. In this research, a novel method to obtain spiral SnS on atomic steps is proposed. Not only high percentage of spiral SnS flakes are achieved, but the nucleation position of spiral SnS could be well controlled. Furthermore, spiral SnS could be grown on artificial steps created on various substrates which gigantically extend its flexibility for application. Finally, contrary to common understanding, spiral SnS turns out to exhibit inversion symmetric structure through the second harmonic generation (SHG) spectroscopy and the cross-sectional TEM analysis. This is the first work to point out that the single spiral morphology with monolayer step height does not guarantee non-centrosymmetric structure in 2D materials.