The exciton-polariton is a kind of boson quasiparticle that is formed by the strong coupling between cavity photons and excitons in semiconductors. The exciton-polariton behaves as a hybrid state of half-light and half-matter and possesses the properties of strong light-matter interaction, low effective mass, large group velocity, long transmission distance, and can be easily controlled. Therefore, it is beneficial to the research and development of new-generation optoelectronic devices such as exciton-polariton lasers, LEDs, photodetectors, spin storage elements, and optical switches. On the other hand, because of the boson properties, when the density of excited particles reaches a certain level, excitons-polaritons can condense into a single macroscopic quantum state (Bose-Einstein condensate) through stimulated scattering. This single macroscopic quantum state bypasses the limit of the particle inversion so that an ultra-low threshold laser can be achieved. Therefore, exciton-polariton has attracted extensive attention of researchers.Previous research mainly focused on the traditional inorganic semiconductor quantum well microcavity systems, and the observation condition requiring low temperature greatly limits its applications. The Two-dimensional Transition Metal Dichalcogenides (TMDs) which emerge in recent years have direct bandgap, strong dipole oscillation strength, large exciton binding energy, van der Waals integration and many other advantages, making them show great potential in exploring the exciton-polariton phenomenon. Furthermore, combining with the valley polarized properties of TMDs, valley-polarized exciton-polariton can be realized to promote the valleytronic applications such as optical spin switches and valley polarized bistable devices.In this review, we systematically discussed the exciton-polariton in two-dimensional TMDs from three aspects. First, the research progress of exciton-polariton in two-dimensional TMDs was discussed. The properties of excitons-polariton in TMDs such as strong nonlinearity, long-distance propagation, and little effect from the dielectric disorder were described. Then the influence of the cavity structure (tunable open Fabry-Pérot cavity and a 3D photonic crystal structure) on the properties of exciton-polariton was discussed. The realization of electrically pumped exciton-polariton was also described in this section. Second, the realization of valley-polarized exciton-polariton in two-dimensional TMDs was reviewed. This section shows that the exciton-polariton in two-dimensional TMDs inherits the valley characteristics of the TMDs excitons. And due to the existence of more relaxation channels, the exciton-polariton has higher degree of valley polarization and valley coherence than those of exciton. By regulating the excitation wavelength and temperature, the degree of valley polarization can be achieved with a value more than 90%. Third, the Bose Einstein condensation of exciton-polariton in two-dimensional TMDs was discussed, including the earliest observation of Bose Einstein condensation of exciton-polariton in 2D TMDs at extremely low temperature and the recent realization of low-threshold exciton-polariton laser at room temperature. At the end of this review, we summarized and analyzed the key scientific and technical issues that need to be solved for the practical applications of two-dimensional TMDs exciton-polariton lasers, such as the understanding of the mechanism of Bose-Einstein condensation, the clarifying of the influence of exciton complex on exciton-polariton condensation, the preparation of two-dimensional gain medium with high-quality and strong emission efficiency, and the construction of high-quality optical resonators as well as the realization of effective coupling between the 2D gain medium and the optical resonator. Finally, we give a brief perspective of the developmentof exciton-polariton lasers based on 2D TMDs materials.