The discovery of quantum spin Hall effect engendered a new chapter of topological materials research in condensed matter physics and materials science. In this talk, I will introduce some of our recent theoretical works about the topological phases in 2D and 3D transition metal chalcogenides. Based on first-principles calculations, we predict monolayer MX2 (M=Mo, W; X=S, Se, Te) of 1T’ structure could exhibit quantum spin Hall effect and their topology can be easily tuned by external electric field, which motivated us to propose a new type of transistor, called topological field transistor. More recently, we found another new class of transition metal chalcogenides MM’Te4 (M=Nb, Ta; M’=Ir, Rh) could be quantum spin Hall insulators in 2D and Weyl semimetals in 3D. [1] X. Qian, J. Liu, L. Fu, J. Li，Science 346, 1344 (2014) [2] J. Liu, H. Wang, C. Fang, L. Fu, X. Qian, Nano Lett. 17 467-475 (2017)