Two methods for Soil conservation in oil palm plantations are by vegetatively and mechanically. Vegetatively method is generally using plants that grow at oil palm plantation such as Asystasia gangetica and Nephrolepis biserrata as cover crop, while mechanically is develop the ridge terrace by cutting the slope. This research aims to determine the role of soil conservation on soil carbon stock, organic matter, and oil palm growth. The research was conducted in mature oil palm plantation (planted year 2005), PTPN VII, South Lampung from August, 2014 until Aprl, 2015. The research used nested design with 6 repetitions nested in each treatment. The treatment consists of a ridge terrace (without and with ridge terrace), and cover crop (without and with cover crop N. biserrata, andA. gangetica). The results showed that the soil conservation application using cover crop and ridge terrace increased carbon stock and soil organic matter compared without soil conservation, respectively of 4.44 t/ha and 0.69%(N. biserrata without ridge terrace); 5.28 t/ha and 0.83%(A. gangetica without ridge terrace); 7.04 t/ha and 1.10%(ridge terrace without cover crop); 10.45 t/ha and 1.64%(N. biserrata with ridge terrace); 11.33 t/ha and 1.78%(A. gangetica without ridge terrace). Soil conservation application also affects the growth of oil palm, especially the average of rachis length and the number of broken leaves.