A method for synthesizing an intergrown twin Ni2Mo6S6O2/MoS2 two-dimensional nanosheet with exposed (00L) crystal planes is disclosed. An Ni—Mo bonded precursor is formed by using an ion insertion method to restrict Ni ions to be located in a lattice matrix of a Mo-based compound; a dinuclear metal sulfide Ni2Mo6S6O2 is formed by precisely adjusting and controlling a concentration of a sulfur atmosphere and utilizing a reconstruction effect of Ni element in the lattice matrix of the Mo-based compound; and meanwhile, a growth direction of Ni2Mo6S6O2 is precisely adjusted and controlled by using a method for growing a single crystal in a limited area, so that Ni2Mo6S6O2 is grown, taking a single crystal MoS2 as a growth template, with the single crystal MoS2 alternately along a crystal plane (110) of the single crystal MoS2, so as to form a twin Ni2Mo6S6O2/MoS2 two-dimensional nanosheet in which Ni2Mo6S6O2 and MoS2 are intergrown.