Abstract-The reflectivity measurement of materials is an innovative application of a reverberation chamber (RC). In this paper we show an analysis of the performance of the reflectivity measurement in an RC in terms of uncertainty of measurement and relevant noise level. The model for reflectivity measurement, which is already present in literature, is based on the absorption cross section (ACS) measurements. If the ACS measurements are averaged with respect to the configurations of the measurement system, then the relevant uncertainty depends only on the number of independent samples. Here, the performance of the reflectivity measurements is shown in cases where it depends only on the number of independent samples acquired in an RC. Simulations and measurements confirm the validity of the expected results.