Characteristics and causation for tropical cyclone (TC) activities over the Western North Pacific (WNP) and the South China Sea (SCS) in 2010 were analyzed by using the data of TCs, reanalysis data of NCEP/NCAR in this paper. TC activities are characterized by (1) forming the least, and the highest percentages of landing, (2) concentrated and westward genesis, (3) higher proportion of strong TCs and short life cycle TCs, (4) the later for the first TC and last TC, and (5) TC landing fewer in July-August and more than normal in September, 5 of 7 TCs landing on Fujian. The causes were studied and the results were listed as follows. Firstly, the warm mode in the East Indian Ocean in 2010 was one of the key extra forcing factors resulting in the least TC genesis in WNP and SCS in 2010, especially the lag response of extratropical atmosphere to El Nino. Secondly， the atmospheric circulation abnormity was the key reasons. It showed the combined impacts of multifactors including the larger and stronger Northwest Pacific subtropical high extending abnormally west, the abnormally westward monsoon trough and 1arge vertical shear anomalies.