In this work we calculate the bands structure for the GeS monolayer from a multi-orbital tight-binding model, where the effect of s-p mixing are considered in slater-Koster equations. The model parameters are adjusting and optimising compared with the band structure obtained by density-functional theory calculation based on the hybrid HSE06 functional. It reproduces the conduction and valence bands as well as the orbital compositions. The anisotropic effective masses and Fermi velocities are identified directly from the anisotropy bands structure.