FTIR spectra were used to measure the spectra information of isoprene. The infrared spectra were calculated by using Gaussian 03 program under density functional (DFT) theory level. The experimental results agree with the theoretical values. The OH-iniated photooxidation of isoprene was conducted by using a smog chamber system made by ourselves. The photooxidation products were detected using FTIR method to study the functional groups and qualitatively analyze the chemical components.The results shown that the photooxidation products contained carbonyl group, C-O bond compounds, aldehyde, ketone, carboxyl acid, and nitric acid compounds.