Abstract: In order to evaluate the stirring efficiency in the reverberation chamber under different stirring modes, and improve the accuracy of the measurement, the method for calculating the number of independent samples which is an important indicator is introduced briefly. The frequencies of 200, 500 and 1000 MHz are chosen to evaluate the stirring efficiency of mechanical stirring and frequency stirring. The calculated number of independent samples shows that the stirring efficiency of the two stirring modes is proportional to the operating frequency. In the mechanical stirring mode, the stirring efficiency can be significantly improved when stirrers work at different speed ratios, and the larger stirring bandwidth is chosen, the higher stirring efficiency can be obtained in the frequency stirring mode, but the number of independent samples has an upper limit in the order of hundreds. Thus the combined stirring method based on mechanical stirring and frequency stirring is proposed, and the stirring efficiency is analyzed deeply, also the formula for calculating the independent samples is given. The test results show that the number of independent samples can be drastically increased under the combined stirring mode.