Radiance detector (RD) is composed of trap detector, interference filter and precision stops. Its radiance responsivity can be traced from the cryogenic absolute radiometer. The absolute spectral responsivity of RD is obtained by measuring absolute responsivity of trap detector, spectral transmittance of filter, gain of trans-impedance amplifier, diameters of field stop and aperture stop and the distance between them, accurately. The overall performance is measured and the uncertainties are evaluated in detail. The combined standard uncertainty in the absolute spectral radiance responsivity calibration is less than 1.26% (confidence probability coefficient k=1), which can meet the high-precision calibration requirement of remote sensors.