Abstract: Ultraviolet A (UVA, 320 nm ~400 nm) induced lipid peroxidation is mainly mediated by reactive oxygen species (ROS) such as singlet oxygen (1O2), superoxide anion (O2(·), hydrogen peroxide (H2O2), and hydroxyl radical (?OH). Among them, O2(· and 1O2 seem to be the precursors of other ROS after UVA radiation. In this study, we aim to discuss the role of 1O2 and O2(·in UVA induced Lipid Peroxidation. A highly sensitive chemiluminescence (CL) probe, 2-methyl-6-(4-methoxyphenyl)-3, 7-dihydroimidazo [1, 2-α] pyrazin-3-one hydrochloride (MCLA) was applied to evaluate the production of O2(· and 1O2 in UVA induced lipid peroxidation in human peripheral lymphocytes. Lipid peroxidation degree was also detected by conventional malondialdehyde (MDA) assay. Experiment results indicate that UVA induced lipid oxidative damage has a positive relationship with 1O2 and O2(· level. The MCLA-dependent CL method can be used to assess the degree of UVA-induced lipid peroxidation quickly and simply.