Presented at the 2014 Aquarius/SAC-D Science Team MeetingThis study demonstrates that the spaceborne Aquarius instrument is able to monitor the sea surface salinity (SSS) variations in the East China Sea (ECS) with the spatial resolution of about 150 km at 7-day interval, where routine observations are difficult. The ascending orbits appear to be affected by unfiltered radiofrequency interference (RFI) much less than the descending tracks. The Aquarius SSS along the ascending tracks is low over the ECS by 0.40 to 0.93 psu (with respect to the in situ CTD data collected during the two separate 7-day periods) and is biased low by 0.41 to 1.07 psu (accuracy, or the time-mean of difference from the regional model along three Aquarius tracks over a 18-month period). The Aquarius data describe well the temporal and spatial variability of the ECS SSS. The temporal trend and magnitude of salinity changes agree remarkably between Aquarius and a regional numerical model, during both the freshwater discharge season from the Yangtze river and the rest of the year. The precision of the Aquarius observation in the ECS is comparable with the Aquarius mission requirement (0.2 psu one-sigma for a monthly average over the open ocean).