Orignal CQDs and functionalized CQDs with SOCl2 (Cl-CQDs ) were prepared in a autoclave, and silver nanoparticles were synthesized using ethylene glycol as a reducing agent. Ag /CQDs and Ag /Cl-CQDs were synthesized by simple mixing respectively. The samples were detected by TEM and FTIR. Fluorescence and absorption spectra were recorded on a fluorescence spectrophotometer and UV-Vis spectrometer, respectively. The results showed that the average diameter of CQDs was about 3.5 nm, and the mean diameter of roundish silver nanoparticles was about 18 nm. Fluorescence quenching happened after incorporating Ag into CQDs, and absorption capacity was strengthen in visible solar wavelength range. Comparing with single Ag and CQDs, Photocatalytic property of composite catalysts became stronger. The composite catalyst with a mass ratio of Ag /CQDs of 1/2 had the highest catalytic efficiency. Ag/Cl-CQDs can promote the degradation of methyl orange, and 50 mL, 50 mg/L methyl orange was degraded in 12 minutes.