The rational cocatalyst design is considered a significant route to boost the solar-energy conversion efficiency for photocatalytic H2 generation. However, the traditional cocatalyst-loading on the surface of a photocatalyst easily leads to scarce exposed active sites induced by the agglomeration of cocatalysts and a hindrance of the light absorption of the photocatalyst, thus significantly limiting the enhancement of the photocatalytic H2-generation performance. Herein, a new concept of uniform-embeddable-distributed cocatalysts is put forward. Consequently, uniform-embeddable-distributed cocatalysts of Ni3S2 were designed and constructed inside and outside of the nanosheet-like ZnIn2S4 photocatalyst to form a Ni3S2/ZnIn2S4 binary system (UEDNiS/ZIS). The unique uniform-embeddable-distributed Ni3S2 cocatalyst (UEDNiS) could provide abundant exposed active sites, facilitate the spatial separation and ordered transfer of charges inside and outside of ZnIn2S4 nanosheets, and reduce the hydrogen-adsorption free energy for photocatalytic H2-generation reactions. As a result, UEDNiS/ZIS exhibited a high photocatalytic H2-generation rate of 60 μmol h-1 under visible-light irradiation, almost 7.8 and 2.8 times higher than pristine ZnIn2S4 and the traditional surface-loaded Ni3S2/ZnIn2S4 (TSLNiS/ZIS), respectively. This work represents a new cocatalyst-design approach to realize high-efficiency hydrogen evolution in binary heterostructured photocatalytic systems.