A new apparatus simultaneously and rapidly measuring the sample radiation and the blackbody radiation by one detector without moving any experimental component is designed to measure the directional spectral emissivity of solid samples in a controlled environment. The effect of multiple reflections in the sample chamber on the measurement result is evaluated. The temperature distribution of the sample surface is measured by using a thermal imager. In order to validate the experimental apparatus, the directional spectral emissivity of silicon is measured in a nitrogen environment and that of iron is measured in vacuum, and the normal spectral emissivity of pure copper is measured during the oxidation process. Good agreement between the measured results and the reported data proves the reliability of the designed apparatus. The expanded uncertainty of the measurement system is estimated to be less than 5.3% when the emission angle is 86°.