Analyses of sea surface height anomalies (SSHA) from Jan. 1993 to Dec. 2001 measured by TOPEX/Poseidon (T/P) satellite altimetry indicate that there are two energy highs of SSHA fluctuations on both sides of the Luzon Strait. The highs centered at (19.5°N, 119.5°E) and (22.0°N, 124.0°E) respectively, are separated by a low energy band in the Strait. Empirical Orthogonal Function (EOF) analysis on the “Far Field” suggests that fluctuations of these two areas are mutually independent. EOF analysis on the “Near Field” shows that SSHA oscillation in the northeastern South China Sea (SCS) is dominated by seasonal variations accompanied with significant intra-seasonal and inter-annual fluctuations. Among which, EOFI and EOF2 reflect 66.7% of the total variance. They are both seasonal but showing three months difference in phase. The basic pattern of EOFI appears to be the seasonal SSHA oscillation centered at (18.0°N, 119.0°E) northwest off Luzon Island, which shows maximums (minimums) in August/Septemb Analyses of sea surface height anomalies (SSHA) from Jan. 1993 to Dec. 2001 measured by TOPEX / Poseidon (T / P) satellite altimetry indicate that there are two energy highs of SSHA fluctuations on both sides of the Luzon Strait. The highs centered at (19.5 ° N, 119.5 ° E) and (22.0 ° N, 124.0 ° E) respectively, separated by a low energy band in the Strait. Empirical Orthogonal Function (EOF) analysis on the “Far Field” suggests that fluctuations of these two areas are mutually independent. EOF analysis on the “Near Field ” shows that SSHA oscillation in the northeastern South China Sea (SCS) is dominated by Seasonal variations accompanied with significant intra-seasonal and inter-annual fluctuations. which, EOFI and EOF2 reflect 66.7% of the total variance. They are both seasonal but showing three months difference in phase. The basic pattern of EOFI appears to be the seasonal SSHA oscillation centered at (18.0 ° N, 119.0 ° E) northwest off Luzon Island, which shows maximums (minim ums) in August / Septemb