A (30-42) ℃ portable ammonia stainless steel heatpipe blackbody source with a front reflector is developed for on site radiance temperature calibration and value dissemination o f infrared ear thermometers.The cavity of the blackbody source is made from an isotherm ammonia heatpipe.The c ylindrical double-cone blackbody source cavity is designed with 60mm in diameter and 272mm in depth. The bottom cone apex angle of the cylindrical double cone cavity is 120°.The aperture of the copper front re flector with a 100° field angle is 20mm.The cavity is paint-coated with an emissivity of 0.95.The STEEP321NIM soft ware based on Monte Carlo method is used to calculate the average plane radiation angle cavity emissivity of the ammonia stainless steel heat pipe blackbody source.The calculated effective emissivities of cavity aper ture plane from 0° to 100° radiation angle are better than 0.999.The PID temperature control system consists of a PI D regulator,highly stable precision platinum resistance thermometer,a DC power supply,and a bimetal temperature sw itch.The blackbody source temperature control enables high reliability.The temperature stability of the b lackbody source is 0.002℃ within 20min and the temperature uniformity of the cavity is 0.03℃.