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The rational cocatalyst design is considered a significant route to boost the solar-energy conversion efficiency for photocatalytic H 2 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 H 2 -generation performance. Herein, a new concept of uniform-embeddable-distributed cocatalysts is put forward. Consequently, uniform-embeddable-distributed cocatalysts of Ni 3 S 2 were designed and constructed inside and outside of the nanosheet-like ZnIn 2 S 4 photocatalyst to form a Ni 3 S 2 /ZnIn 2 S 4 binary system (UEDNiS/ZIS). The unique uniform-embeddable-distributed Ni 3 S 2 cocatalyst (UEDNiS) could provide abundant exposed active sites, facilitate the spatial separation and ordered transfer of charges inside and outside of ZnIn 2 S 4 nanosheets, and reduce the hydrogen-adsorption free energy for photocatalytic H 2 -generation reactions. As a result, UEDNiS/ZIS exhibited a high photocatalytic H 2 -generation rate of 60 μmol h -1 under visible-light irradiation, almost 7.8 and 2.8 times higher than pristine ZnIn 2 S 4 and the traditional surface-loaded Ni 3 S 2 /ZnIn 2 S 4 (TSLNiS/ZIS), respectively. This work represents a new cocatalyst-design approach to realize high-efficiency hydrogen evolution in binary heterostructured photocatalytic systems.