As an important land cover type of Earth's surface, the surface water has a huge effect on the water cycle, climate change, environment and human activities. Thus, it is significant to analyze the distribution of the surface water and its change trend in time series. This study focuses on the use of the Automated Water Extraction Index (AWEI) to quantitatively evaluate the total surface water area in South America based on Landsat TM imagery and the MODIS digital product acquired in 2011. Meanwhile, the seasonal area fluctuation of the surface water in each typical climatic zone is monitored and the resultant data is used to analyze why the fluctuation occurred. The known data show that the total area of surface water in South America, mainly concentrated in the Amazon River basin, the Parana River basin and the Patagonia Plateau, is 305,000 km2 and the water rate is 1.69%. Based on our study, the number of lakes in South America is 9,579 while the total area is 142,000 km2, which takes 46.42% of the total area of surface water; the area of waterways is 157,000 km2, which takes 51.56% of the total area of surface water; and the reservoirs and ponds, which takes 2.01% of the total area surface water, is 6144.8 km2. From the perspective of climate zones, the area of surface water in the tropical zone of South America was influenced obviously by the change of rainy seasons, and within which the tropical desert climatic zone was the most affected one; in the temperate zone, the area of surface water didn’t change a lot because it has distinct seasons; in the plateau mountain climate zone, the area didn’t change a lot due to its unique climate feature; in both subtropical monsoon wet climate zone and Mediterranean climate zone, the surface water hardly changed with seasons but it exhibited obvious variations in winter and summer seasons. From the perspective of countries in South America, Brazil has the largest area of surface water (147,000 km2) which takes 48.17% of the total area of surface water in South America and its water rate was 1.72%; Argentina has the second largest area (34,000 km2) which takes 11.24% of the total surface water area and its water rate was 1.23%; while, Venezuela has the largest water rate (3.08%). The surface water in each typical climatic zone of South America has seasonal area fluctuation on several levels, which may relate to climate change and human activities. Further studies are needed to explain this issue in future.