Four　kinds　of　CdS　quantum　dots　(Qds)　with　four　different　surface-capping　organic　groups　were　prepared　by　a　colloidal　chemical　method.　The　linear　and　nonlinear　optical　properties　of　the　materials　were　characterized　using　transmission　electron　microscopy　(TEM),　ultraviolet-visible　(UV-Vis)　absorption　spectroscopy,　photoluminescence　(PL)　spectroscopy,　and　Z-scan　measurements.　The　results　show　that　the　particle　size,　the　surface　morphology,　and　the　defect　concentration　are　the　main　factors　that　determine　the　nonlinear　optical　properties.