Abstract: The spectral efficiency of the downlink of multi-user multiple-input and single-output (MU-MISO) was analyzed in the time-division duplex (TDD) communication systems with large-scale antennas. Assuming that the number of users was fixed and the antenna number (M) of base station (BS) increases without limit, the conclusions through theoretical derivations and analyses were drawn that, when the transmit power of the BS reduces to 1/M of that of BS with single antenna, the system spectral efficiency tends to a constant value with the increase of M if the BS acquires the perfect channel state information (CSI). The adverse effects of the inter-user interferences and the fast fading could also be eliminated through simple pre-processings. Although the multicell system is affected by the pilot contamination, which is the reason why the inter-cell interferences cannot be eliminated, the reduced transmit power makes the system changed from interference-limited to noise-limited. The limit expression of the system spectral efficiency using zero-forcing (ZF) normalized precoding is equal to that using maximum ratio transmission (MRT) normalized precoding. Finally, the lower bound of the spectral efficiency of multi-user downlink applying space time block code was presented and the correctness of the above conclusions was confirmed by the simulation analyses.