Based on the Kirchhoff's law,an experimental apparatus for emissivity measurement at intermediate and high temperatures is developed,in which the double-light-path contrast measurement technique is used. The apparatus consists of three parts:the sample heating system,the signal detection and processing system,and the display system. With this apparatus,the emissivities of two standard samples (polished steel and roughened steel) are measured at different temperatures. The emissivity data of these two samples are fitted to the analytical function with the least-squares method. The measurement uncertainty of this experimental apparatus is analyzed. As a result,over the temperature range from 800 K to 1100 K,the largest emissivity uncertainty of the polished steel is σε=4.26×10-3,and the corresponding uncertainty of temperature measurement is σT=0.497 K,σT/T=0.0611%;the largest emissivity uncertainty of the roughened steel is σε= 3.80×10-3,the corresponding uncertainty of temperature measurement is σT=0.415 K,σT/T= 0.0507%.