Fabrication of semiconductor composites consisting of multicomponent or multiphase heterojunctions is a very effective strategy to design highly active photocatalyst systems. Here we present a facile design to fabricate novel CdS/ZnS heterostructured porous sheet-like nanocomposite based on a cation-exchanged hydrothermal procedure. Micro-structural analyses reveal that the product is a kind of heterostructured composite with porous structure and high crystallinity. The composite nanosheets exhibited enhanced visible-light photoactivity compared with pure ZnS or CdS. Among them, sample of Cd0.45Zn0.55S gave the highest degradation rate of about 99% under visible-light irradiation within 60 min when 10 mg of the sample was added into 50 mL of methyl orange in aqueous solution (10 mg/L). The enhanced photocatalytic activity was presumed to result from the direct photoinduced interfacial charge transfer (IFCT) from the valence band (VB) of ZnS to CdS.