The ZnSe/SiO2 composite thin films were prepared by sol-gel process a nd in-situ growth technique. X-ray diffraction results showed that the phase str ucture of ZnSe particles embedded in ZnSe/SiO2 composite thin films i s the sphalerite (cubic ZnS). X-ray fluorescence results revealed that the molar ratio ofZn/Se is about 1∶1.01—1∶1.19. Scanning electron microscopy results r evealed that the size of ZnSe crystal particles is about 400nm, while some parti cles are less than 100nm in size. The dependence of ellipsometric angle Ψ, Δ w ith wavelength λ of ZnSe/SiO2 composite thin films was investigated with spectroscopic ellipsometers. The optical constant, thickness, porosity and the concentration of ZnSe in ZnSe/SiO2 composite thin films were fitt ed according to Maxwell-Garnett effective medium theory. The photoluminescence p roperties of ZnSe/SiO2 composite thin films were investigated with fl uorescence spectrometer. The photoluminescence results indicated that the emissi on peak at 487nm under 395nm excitation corresponds to the band-to-band emission of sphalerite ZnSe crystal. The strong free exciton emission and other emission peaks correlated with ZnSe lattice defect were also observed.