The invention discloses a two-dimensional transition metal disulfides (TMDs) monocrystalline, and a preparation method and applications thereof. According to the preparation method, in an inert atmosphere, assist control of the concentration of S or Se in a system is realized with common metal which is capable of reacting with sulfur family elementary substance (S, Se) and hydrogen so as to control sulfuration degree or selenylation degree of a transition metal layer, and controllable growth of TMDs monocrystalline is realized via chemical vapor deposition; deposition temperature is controlled to be 750 to 850 DEG C, and deposition time is controlled to be 5 to 15min so as to complete TMDs monocrystalline preparation; wherein, strict control on high-quality two-dimensional transition metal disulfides monocrystalline is realized via optimization of preparation parameters such as substrate sputtering treatment method, sulfur family elementary substance powder using amount, absorbed S/Se metal area and kinds, hydrogen concentration, growth temperature, and growth time.