In the Southeast US, changing climate conditions are predicted to be warmer and more severe drought in the summer. The largest pool of carbon on land is contained in soils and it can change in response to changing climate. Many studies have shown priming effect of soil carbon in top soils, however, little is known about deep soil carbon. The aim of this paper is to study the effect of wetting/drying cycles on deep soil carbon in a southeastern US loblolly pine plantation. A carbon incubation experiment with wetting/drying cycles was established using soil samples taken from Taliaferro, GA. Soil were sample in 8 depths: 0-10, 10-20, 20-50, 50-100, 100-150, 150-200, 200-250 and 250-300 cm. Results show that top soil has high carbon mineralization peak in response to wetting/drying cycles, however, deep soil carbon mineralization rate changed significantly. In consideration of soil moisture, this study indicates that total soil carbon would decrease under more severe wetting/drying cycles and release more CO₂ into the atmosphere, which could aggravate climate change.