A portable infrared spectral radiance measurement apparatus without the cooling based on PbSe detectors is designed to measure the spectral radiance of the object in the wavelength range from 2.1 to 4.1 μm. Cores Luxell 256 module is applied which integrates 256 pixel line array PbSe detectors, amplifiers, analog-to-digital convertors, and Universal Serial Bus output interface. Electric aperture is applied to eliminate the effect of temperature drift. Wavelength and response function of the apparatus is calibrated with the blackbody. Results show that the wavelength resolution is 10 nm. The relative error of measured spectral radiance is below 2.3%.