The invention discloses a preparing method of porous monocrystal IT MoS2 nanosheet. The method comprises the steps of 1, preparing 2H crystal form MoS2 nanosheet using hydrothermal method; 2, conducting stripping of multi-layered 2H crystal form MoS2 nanosheet with ultrasonic wave and assisting with a lithium-ion intercalation method. The 1T MoS2 nanosheet can be directly used for electro-catalysis hydrogen production, and compared with MoS2 with other structures, electro-catalysis hydrogen production property can get fast improvement, porous structure provides more edges for the catalysis, therefore can expose more active sites, which is beneficial to electro-catalysis hydrogen production; single-layered structure enables larger specific surface area of the catalyst, can provide more reaction active sites. Compared with a multi-layered structure, a single-layered structure reduces electric transmission resistance between layer and layer, is beneficial to transmission and transfer of electricity, thus accelerating velocity of electro-catalysis hydrogen production.