Two-dimensional transition metal dichalcogenides (TMDs) such as MoS2 have different optical and electrical properties with the change of thickness and layer number, and exhibit unique excitonic behavior and high optical quantum efficiency, thus they have great potential applications in optoelectronic devices. Recently, there are great progresses on the studies of optical properties and related optoelectronic devices of TMDs. For example, the photoluminescence (PL) of TMD materials can be modulated through the electric field, chemical doping and defects engineering, and the PL quantum efficiency is greatly enhanced. The LEDs based on lateral and vertical heterojunctions stacked by TMD materials are extensively investigated and the high light emission efficiency is demonstrated. The laser emission with low threshold is also realized using TMDs as gain medium and integrated with micro disk and photonic crystals. This review starts from the structures and optical properties of TMDs, summarizes PL modulation methods and effects of TMD materials, introduces the research progresses of laser emission of TMDs, and finally the laser future development based on TMDs is prospected.