A　hierarchical　nanosphere　assembled　by　CdS　nanorods　was　fabricated　via　a　simple　one-pot　hydrothermal　route　using　(NH4)(2)MoS4,　Cd(NO3)(2)　and　ethanediamine　as　the　initial　reactant.　The　synthesized　samples　were　characterized　by　X-ray　diffraction,　field-emission　scanning　electron　microscopy,　transmission　electron　microscopy　and　X-ray　photoelectron　spectroscopy.　According　to　control　experiments,　it　can　be　deduced　that　the　(NH4)(2)MoS4　and　ethanediamine　may　be　predominantly　responsible　for　the　formation　of　hierarchical　architecture,　and　a　potential　mechanism　based　on　cation　exchange　reaction　was　proposed.　For　further　investigation　of　the　photocatalytic　performance　of　the　as-prepared　samples,　photocatalytic　water-splitting　experiment　was　carried　out.　The　hierarchical　CdS　synthesized　in　the　origin　mol　ratio　of　Mo:　Cd　=　0.3:　1.4　exhibited　the　best　performance　for　photocatalytic　water　splitting,　and　the　hierarchical　CdS　with　unique　morphology,　compared　with　the　isolated　CdS　nanorod,　showed　an　enhanced　photocatalytic　activity　for　water　splitting　arising　from　the　intimate　contact　among　CdS　nanorods,　incremental　specific　surface　area　and　the　high　ratio　of　(002)/(100).　Graphical　Abstract　A　hierarchical　nanosphere　assembled　by　CdS　nanorods　was　fabricated　via　cation　exchange　reaction　and　showed　a　superior　photocatalytic　water-splitting　activity　than　isolated　CdS.