Eleven years of sea surface height from satellite altimetry data are used to describe the low frequency variability of South China Sea (SCS) surface circulation through Empirical Orthogonal Function (EOF) analysis. The annual variability clearly agrees with previous studies, revealing the SCS response to seasonal fluctuations of the overlaying monsoon winds. The summer eastward jet off west coast of SCS is shown from the second seasonal EOF mode. Two new patterns of year-to-year and decadal variability are presented for the first time from measurements. Long term positive trend appears from 1993 to 2001 and reverses the sign of its trend again from 2001 to 2003. Abnormal events occur in 1994--1995, in 1997--1998 and in 2002 with different spatial scales regarding both basin-scale distribution and meso-scale variability located off the western SCS. Association of these events with the El Ni¿o-Southern Oscillation is discussed.