A portable standard source for skin type clinical thermometers was developed at CMS for fulfilling industrial and medical demands. It contains a modified a high quality blackbody with large size opening aperture which with large heat capacity and high emissivity. The blackbody is surrounded with heaters and the walls provide good heat conduction. In addition; the horizontal type blackbody was also restricting any excessive air convection. The temperature was measured with thermistors which were calibrated according to the International Temperature Scale of 1990 (ITS-90). The blackbody was designed at two fixed temperature points (38°C and 30°C). The long term temperature stability of the portable blackbody for two hour at 38°C is ±0.0007°C and at 30°C is ±0.0011°C which operation ambient temperature was within (22 + 1)°C. The emissivity of the blackbody is designed at 0.95. For converging factor (k) equals to 2, the uncertainties of the whole standard blackbody system, without device-under-test (DUT), at 30°C and 38°C are 0.046°C and 0.059°C, respectively, which were also traceable to ITS-90.