A new procedure for evaluating the effective spectral emissivity of a blackbody radiator, the "Temperature Uniformity Free Procedure" (TUFP) has been developed at NIM in the past two years. Besides having the advantage of independence of the temperature distribution of the radiators, the new procedure can be conveniently used in conducting the evaluation of blackbody radiators in situ. Estimates for several cases in this paper have demonstrated that the proposed procedure can provide a precise evaluation of practical blackbody radiators. An experiment setup was built to test the procedure that included a temperature-control led blackbody radiator, a radiation thermometer with four working wavelengths and a calibration system. The experiments verified the validity of the proposed procedure for evaluating the effective spectral emissivity.