The　semiconductor　quantum　dots　(QDs)　can　be　very　efficient　to　tune　the　response　of　photocatalyst　of　TiO2　to　visible　light.　In　this　study,　CdS　QDs　formed　in　situ　with　about　8　nm　have　been　successfully　deposited　onto　the　surfaces　of　TiO2　nanotubes　(TNTs)　to　form　TNTs/CdS　QDs　nanocomposites　by　use　of　a　simple　bifunctional　organic　linker,　thiolactic　acid.　The　diffuse　reflectance　spectroscopy　(DRS)　spectra　of　as　prepared　samples　showed　that　the　absorption　edge　of　the　TNTs/CdS　composite　is　extended　to　visible　range,　with　absorption　edge　at　530　nm.　The　photocatalytic　activity　and　stability　of　TNTs/CdS　were　also　evaluated　for　the　photodegradation　of　rhodamine　B.　The　results　showed　that　when　TNTs/CdS　QDs　was　used,　photocatalytic　degradation　of　RhB　under　visible　light　irradiation　reached　91.6%,　higher　than　45.4　and　30.5%　for　P25　and　TNTs,　respectively.　This　study　indicated　that　the　TNTs/CdS　QDs　nanocomposites　were　superior　catalysts　for　photodegradation　under　visible　light　irradiation　compared　with　TNTs　and　P25　samples,　which　may　find　wide　application　as　a　powerful　photocatalyst　in　environmental　field.