2D SnS2 crystals are attracting increasing attention owning to the huge potential for electronic and optoelectronic applications. However, batch production of 2D SnS2 crystals via a simple vapor process remains challenging by far. Moreover, the growth mechanism for vapor growth of 2D SnS2 is not well documented as well. Herein, a simple approach is presented for preparation of large-scale 2D SnS2 crystals on mica sheets and it is demonstrated that these 2D crystals follow a screw-dislocation-driven (SDD) spiral growth process. The synthesized 2D crystals show hexagonal and truncated triangular shapes with the lateral size ranging from a few micrometers to dozens of micrometers. Observations of key features for screw dislocations, such as helical fringes, dislocation hillocks, and herringbone contours, solidly confirm the SDD spiral growth behavior of the SnS2. Possible mechanism is proposed in this work to show the generation and propagation of screw dislocations. Furthermore, in order to explore the optoelectronic property of the SnS2, photodetectors based on 2D SnS2 crystals are fabricated. The resulting device shows excellent operating characteristics, including good photo-stability and reproducibility as well as a fast photoresponse time (approximate to 42 ms), which enable the SnS2 a promising candidate for photodetectors.