Objective: To investigate the expression of OX40 ligand(OX40L) on C-reactive protein(CRP)-triggered mouse aorta endothelial cells (MAECs) in vitro. Methods: MAECs from aorta were isolated by digestion with collagenase typeⅡ. The cell growth was confirmed by morphological characteristics and the immunological marker, factor Ⅷ(or Willebrand factor, vWF). The expression of OX40L by MAECs was detected by RT-PCR and western blot after incubating with 100μg/ml CRP for 48 hours. Results: Twenty-day cultures of MAECs formed confluent monolayer of a cobblestone pattern. RT-PCR and western blot assay showed that the level of OX40L expression in MAECs receiving CRP treatment was higher than control. Conclusion: A reliable method is described to isolate and propagate MAECs. CRP upregulates OX40L expression in MAECs.