The seasonal variability of the significant wave height(SWH) in the South China Sea(SCS) is investigated using the most up-to-date gridded daily altimeter data for the period of September 2009 to August 2015. The results indicate that the SWH shows a uniform seasonal variation in the whole SCS, with its maxima occurring in December/January and minima in May. Throughout the year, the SWH in the SCS is the largest around Luzon Strait(LS) and then gradually decreases southward across the basin. The surface wind speed has a similar seasonal variation, but with different spatial distributions in most months of the year. Further analysis indicates that the observed SWH variations are dominated by swell. The wind sea height, however, is much smaller. It is the the largest in two regions southwest of Taiwan Island and southeast of Vietnam Coast during the northeasterly monsoon, while the largest in the central/southern SCS during the southwesterly monsoon. The extreme wave condition also experiences a significant seasonal variation. In most regions of the northern and central SCS, the maxima of the 99 th percentile SWH that are larger than the SWH theoretically calculated with the wind speed for the fully developed seas mainly appear in August–November, closely related to strong tropical cyclone activities.Compared with previous studies, it is also implied that the wave climate in the Pacific Ocean plays an important role in the wave climate variations in the SCS. The seasonal variability of the significant wave height (SWH) in the South China Sea (SCS) is investigated using the most up-to-date gridded daily altimeter data for the period September September to August 2015. The results indicate that the SWH shows Throughout the year, the SWH in the SCS is the largest around the Luzon Strait (LS) and then through southward across the basin. The surface wind speed has a similar seasonal variation, but with different spatial distributions in most months of the year. Further analysis indicates that the observed observed SWH variations are dominated by swell. It is the largest in two regions southwest of Taiwan Island and southeast of Vietnam coast during the northeasterly monsoon, while the largest in the central / southern SCS during the southwesterly monsoon. The extreme wave condition also exper In most regions of the northern and central SCS, the maxima of the 99th percentile SWH that are larger than the SWH theoretically calculated with the wind speed for the fully developed seas primarily appear in August-November, closely related to strong tropical cyclone activities. Compared with previous studies, it is also implied that the wave climate in the Pacific Ocean plays an important role in the wave climate variations in the SCS.