Hohlraum radiation temperature is an important parameter for inertial confinement fusion (ICF) research. Experimental measurements of radiation temperature by a streaked optical pyrometer and a soft X-ray spectrometer (SXS) with 14 absolutely calibrated channels are performed on SG-Ⅱ laser facility,which shows that the results of the two methods agrees with each other well. With 2.1kJ laser energy and 1ns pulse width, the hohlraum radiation temperatures for small hohlraum (Φ0.8 mm×1.7 mm, LEHΦ0.38 mm) and large hohlraum (Φ1.0 mm×2.1 mm, LEHΦ0.6 mm) are 180 eV and 150 eV, respectively. Using a sampling-based method (Monte Carlo), an uncertainty analysis program-package is set-up for SXS. After precise calibration and improvements for several components in SXS, the relative uncertainty of radiation temperature is significantly reduced from 8% to 3%.