Funded by the National Key Basic Research Development Program, a multi-vessel oceanography survey was conducted synoptically in the South China Sea (SCS) in August 2000, which appeared to be the unique, available synoptic survey that covered the entire SCS basin in deep summer. A number of difficulties were encountered during the survey that affected the quality of observation, even though they were resolved underway. Although some related research works were previously published, no carefully quality control of the data and a comprehensive analyses had ever appeared before. In this work, the original CTD and shipboard ADCP data were carefully calibrated in the first place, and the hydrography and circulation features were then analyzed and discussed to leave a record of the cruises as complete as possible. The results indicate that, in deep summer, the basin shows different physical characteristics on both sides of its SW–NE oriented axis of the basin. The circulation is generally anticyclonic southeast of the axis, in which the Nansha anticyclonic gyre (NSAG) is especially powerful; the area northwest of the axis, in contrast, appears to be dominated by mesoscale features of different categories, where no obvious structure of large scale circulation is found. The analyses confirm that the scales of the NSAG are over 400 km horizontally and nearly 1000 m vertically, with a maximal swirling speed close to 1 m/s, which appears to be the most remarkable circulation feature of the SCS. Moreover, its position and strength are subject to significant interannual variation. In the Mindoro Strait, the exchange flow showes a sandwich structure during the observation period. This is different from our previous understanding and suggests that the strait exchange may have different modes varying with the forcing condition.