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