Abstract For testing the sensitivity of plumbicon used in x-ray camera a P20 type light source is required. There are two methods of getting P20 type light source: (1) The P20 type light source is composed of a mini-oscillotron, screen of which is coated with P20 type phosphor, and four power supplies. (2) The P20 type light source is obtained by adding three particular filters to an A light source. The performance of two sources obtained by different methods are compared.