Aiming at the loaded effect of reverberation chamber, the lossy approaches in cavity are analyzed, and it is concluded that the loaded lossy is the only controllable approach in the testing process. Then five test scenarios are constructed to estimate the quality factor of reverberation chamber by using the time domain method. The result shows that the lossy effect caused by metal antenna supports is the least, while the non-metallic antenna supports could significantly load the reverberation chamber and reduce the quality factor of reverberation chamber. With the increase of the number of non-metallic supports, the effects would become more obviously. In addition, the average absorption cross section of the load is also investigated, taking all the lossy objects in the reverberation chamber as one lossy absorption cross section. It is shown that the absorption cross section of the metal antenna support is the smallest, and the loading absorption cross section of the non-metal support is significantly increased.