A new assay of protein kinase A using capillary electrophoresis has been established.It is a universal and useful method for kinase activity. The method based on principle that substrate (kemptide)and product (phosphorylated kemptide) are easily seperated by capillary electrophoresis and the enzyme activity can be calculated on the integrated area. A continous sampling technique which can analyse more than 10 samples in one run has also been developed.The new method is easy to operate and its accuracy and sensitivity are higher than that of conventional isotopic method.