Porous　ZnIn2S4　microspheres　have　been　successfully　synthesized　by　means　of　a　facile　thermal　solution　method　at　353　K.　This　method　was　a　simple　route　that　involved　low　temperature,　no　templates,　no　catalysts,　no　surfactants,　or　organic　solvents.　Scanning　electron　microscopy,　transmission　electron　microscopy,　high-resolution　transmission　electron　microscopy,　X-ray　diffraction,　energy-dispersive　X-ray　spectroscopy,　X-ray　photoelectron　spectroscopy,　nitrogen　sorption　analysis,　and　a　UV-vis　spectrophotometer　were　used　to　characterize　the　products.　The　results　demonstrated　that　the　microspheres,　which　were　composed　of　many　ZnIn2S4　single　crystal　nanosheets,　underwent　the　Oswald　ripening　and　self-assembly　processes.　A　morphology　formation　mechanism　has　been　proposed　and　discussed.　The　porous　ZnIn2S4　product　showed　an　enhancing　visible-light　photocatalytic　activity　for　methyl　orange　degradation.　The　as-grown　architectures　may　have　potential　applications　in　solar　energy　conversion,　environmental　remediation,　and　advanced　optical/electric　nanodevices.