Abstract: Taking the phenomenon whether the earthquakes with M≥5.5 occur or not as the sign, the seismically active and quiet periods can be divided in the South China region. The research results show well the consistency with the time change trend of stress modulation of seismic frequency (≥M_L 2.0). Besides, the features of seismic frequency during the active and quiet periods are obviously different. Before the moderately strong earthquakes in the region there are frequent seismic activity with magnitude of 4 or so and small earthquake swarms. The moderately strong earthquakes in South China region are related to occurrence of earthquakes with magnitude of 7 or so in Yunnan region. According to the statistical corresponding relation between seismicity in Taiwan and South China regions since 20^th century, it is found that the corresponding rate of moderately strong earthquakes in South China to the earthquakes with magnitude of 6 or so in western Taiwan occurred in one year is 0.5; and the corresponding rate of moderately strong earthquakes in South China to the earthquake with magnitude of 7 or so in two years is 0.3. The corresponding regions include Taiwan straight, Fujian Province and eastern Guangdong areas, and Guangxi and Beibu Bay areas are also involved. Compared with M_S 6 earthquakes, the Taiwan M_S 7 earthquakes show larger effected range.

Key words: Feature of seismic activity, Seismically active and quiet periods, Influence from Taiwan strong earthquakes, South China region