The construction of high-performance and stable nanocomposite photocatalyst remains a great challenge toward photocatalytic hydrogen evolution reaction, which is mainly due to the mediocre interfacial contact between the cocatalyst and the host. In this work, ultrasmall NiS is highly dispersed on HNb3O8 2D nanosheet via a facile electrostatic adsorption/self-assembly process. Interestingly, the growth of NiS is greatly suppressed by the interlayered spatial steric inhibition effect and a strong interaction between NiS and HNb3O8 nanosheet is formed. While the modification of NiS by the traditional methods, such as the coprecipitation and mechanical mixing methods, could not generate the sub-nanometer size of NiS with the tight contract between NiS and HNb3O8 nanosheet. As a result, the recombination of the photogenerated carriers is greatly suppressed on the sample prepared by our method. Furthermore, the overpotential of hydrogen evolution reaction could also be reduced significantly. Thus, the as-prepared composite exhibits a markedly improved photocatalytic H-2 evolution activity as well as considerable stability. The optimal sample shows the H-2 evolution rate of 1519.4 mu mol g(-1) h(-1), which is about 17.4 times higher than that of the bare HNb3O8 nanosheets. The activity is also a magnitude higher than that of the sample prepared by a mechanical mixing method. Additionally, NiS/HNb3O8 prepared by the developed method shows a comparable activity as well as overpotential with Pt/HNb3O8, indicating an alternative to platinum.