Autoradiograph assay of p38 MAPK (mitogen-activated protein kinase) activity was established, and applied in measurement of p38 MAPK activity of vascular endothelial cell stimulated by lipopolysaccharide (LPS). Results showed that autoradiograph assay possessed specificity and sensitivity. Activity of p38 MAPK in endothelial cell treated by LPS was increased at 15 min, and reached maximum value during 30～60 min,then descended. It suggested that domestic laboratory completely had the ability to establish autoradiograph assay of kinase activity,and applied in study of signal transduction.