In this study, a new reflective experimental apparatus, which can measure the spectral emissivity of opaque materials accurately and real timely, has been developed based on the Kirchhoff's law by using the GaAs semiconductor laser as the standard radiation source. The spectral emissivity of brass and red copper at wavelength λ=1.55 μm were investigated systematically with the temperatures range from 300 up to 1123 K by using this apparatus and the influence of temperature, oxidation and heating time on the spectral emissivity of two kinds of specimens were also discussed. The experimental data showed that the spectral emissivity increased with increase of temperature and appeared its peak value and valley value when the thickness of oxide film was at some degree. The spectral emissivity of red copper was always greater than that of brass. The formula for calculating the thickness of oxide film was derived from the reflection model composed of a metal and oxide film, then the peak and valley thickness of the red copper were estimated according to this model. The experimental data of constant temperature measurements showed that the spectral emissivity had a slight increase with heating time increasing. Two hours later, the spectral emissivity of two kinds of samples trended to be stable when the thickness of oxide film was at some degree. The values of spectral emissivity at high temperatures were always larger than that of low temperatures. The results of this study will further enrich spectral emissivity data of copper and provide experimental basis for its application.