The application potential of thermal radiation measurements in energy harvesting, infrared stealth, and radiative cooling has stimulated renewed research interest in this domain. However, the precise measurement of thermal radiation in laboratory settings encounters challenges stemming from the emission of thermal radiation by optical components and the surrounding environment. In this study, a measurement method was devised to segregate the backgrounds of optical components and sample signal, thereby facilitating accurate measurement of the infrared spectral emissivity of samples at room temperature and higher. Calibration of sample measurement temperatures was accomplished through the fitting of measured spectra of sample with Planck theoretical spectra. To validate the measurement method, a Pt/Cr/Si emitter was conceived and fabricated. The spectral emissivity of the sample, as measured, exhibited commendable concordance with simulation results, underscoring the efficacy of the measurement approach.