An　insurmountable　problem　for　silver-based　semiconductor　photocatalysts　is　their　poor　stability.　Here,　atroom　temperature,　AgI　with　different　concentrations　(5%,　10%,　20%　and　30%)　were　coupled　into　Ag　2　CO　3　,producing　a　series　of　novel　AgI/Ag　2　CO　3　composite　photocatalysts.　The　effects　of　AgI　addition　on　theAg　2　CO　3　catalyst　for　photocatalytic　degradation　of　methyl　orange　(MO)　under　visible　light　irradiation　havebeen　investigated.　Some　physicochemical　technologies　like　N2physical　adsorption/desorption,　powderX-ray　diffraction　(XRD),　scanning　electron　microscopy　(SEM),　transmission　electron　microscopy　(TEM),energy-dispersive　X-ray　(EDX)　spectroscopy,　X-ray　photoelectron　spectroscopy　(XPS),　and　UV-vis　diffusereflectance　spectroscopy　(UV-vis　DRS)　were　applied　to　characterize　these　products.　Results　show　thatthe　photocatalytic　degradation　activity　of　AgI/Ag　2　CO　3　photocatalyst　is　much　higher　than　that　of　pure　AgIand　Ag　2　CO　3　.　With　the　optimal　content　of　AgI　(20　wt%),　the　AgI/Ag　2　CO　3　exhibits　the　highest　photocatalyticdegradation　efficiency.　Its　first　order　reaction　rate　constant　(0.54　h-1)　is　20　times　of　that　of　AgI　(0.026　h-1)and　3.6　times　of　that　of　Ag　2　CO　3　(0.15　h-1).　The　characterizations　and　theory　calculation　show　that　AgI　andAg　2　CO　3　have　suitably　matched　band　gap　structures.　The　formation　of　AgI/Ag　2　CO　3　heterojunction　withintimate　interface　could　effectively　increase　the　separation　efficiency　of　the　e-/h+pairs　and　promotethe　production　ofOH　and　O　2　-radicals,　which　brings　about　the　fast　degradation　rate　of　the　dye　and　anincrease　in　photocatalytic　stability.