Based on different fertilization treatments in Yanting Purple Soil Agro-Ecological Experimental Station for a long period, the effects of two forms of exogenous organic materials (pig manure composting and straw returning) on the contents of soil organic carbon, total nitrogen, total phosphorus, nitrate nitrogen and available phosphorus were explored, and soil organic carbon components were analyzed by ¹³C nuclear magnetic resonance spectroscopy (¹³C-NMR). The results showed that organic materials addition significantly increased the contents of soil organic carbon and nutrients in 0-30 cm soil, the contents of organic carbon, total nitrogen, total phosphorus, available phosphorus and nitrate nitrogen increased by 22.13%-100.15%, 28.98%- 84.29%, 18.33% -94.17%, 38.52%-152.36% and 219.45%-741.78%, respectively. The effects of pig manure compost on the contents of total phosphorus, available phosphorus and nitrate nitrogen in soil were greater than those of straw returning. Both pig manure and straw addition caused changes of soil organic carbon components of tilled soil (0-20 cm), which increased the proportions of alkoxy carbon and carboxyl carbon and decreased the proportion of alkyl carbon at 0-10 cm soil, while increased the proportion of carboxyl carbon but increased the proportion of alkyl carbon at 10-20 cm soil. In conclusion, long-term addition of organic materials can significantly improve the organic carbon pool and its stability of dry farmland in hilly areas of central Sichuan. This work could provide scientific reference for evaluation of carbon sink function.