Soil carbon is sensitive to changes in climate conditions. This study aims to determine potential climate change effects on soil carbon stock across Louisiana's watersheds using a soil carbon model integrated with geographical information system. Three climate change scenarios were projected based on the Hadley model outcome: 1) a 4 °C increase of air temperature with a -12.9 mm/month reduction of precipitation; 2) a 2.5 °C increase of air temperature with a -10.0 mm/month reduction of precipitation and 3) a 1.5 °C increase of air temperature with a -7.8 mm/month reduction of precipitation. The climate change scenarios served as ambient environment conditions for the modeling environment, and the RothC model was used to estimate soil carbon emission from different soil types under different land use activities. This paper presents the modeling results and discusses the effects of changes in temperature and precipitation on soil carbon stock across Louisiana's watersheds. Furthermore, the study evaluates applicability of the RothC model in large-scale soil carbon modeling.