As2S3 is a semiconductor, which is known as a layer crystal with structure that is very similar to the metal chalcogenides, such as MoS2 and graphite. In such crystalline structure, the molecular unit is extended in two dimensions indefinitely. The unit cell of As2S3 contains two layers with bond length of 2.24A within the layer and 3.56A between the layers. Large difference between interlayer and intralayer bond length corresponds to a significant difference in bond strengths. The weak bonding between layers primarily occurs via van der Waals interactions. Optical phonons in 2D layer crystal As2S3 have been investigated by Raman scattering in temperature range of 4K-270K in two polarizations in the layer plane (ac plane). Our experimental data shows strong polarization dependence of Raman bands in ac plane for internal mode (intra-layer interactions). Additionally, it presents low frequency band, due to the weak inter-layer interaction. The important evidence for the dominance of layer symmetry with very weak interaction between the layers provides understanding of structural motives of As2S3 and may predict optical / electronic properties of similar 2D materials.