【Objective】Carbon (C) is a major component of soil organic matter, and crop residues are the main source of soil organic C (SOC). A large volume of studies have demonstrated that straw incorporation into the field is conducive to accumulation of soil organic matter and build-up of soil fertility. However, it is still not yet very clear how incorporation of corn stalk and stubble affects distribution and fixation of SOC in soils different in fertility, and how much extraneous new C contribute relatively to SOC. Once extraneous new carbon is amended into soil, it is very hard for researchers to distinguish new carbon from native organic carbon in the soil with traditional techniques. Therefore the stable isotope labeling technique is applied to an in-lab incubation experiment to explore for differences between soils different in fertility in distribution and fixation of extraneous new carbon after incorporation of corn stalk and stubble. 【Method】Soil samples were collected from the topsoil layers (0~20 cm) of two fields different in soil fertility, LF and HF in the long-term experimental station of the Shenyang Agricultural University, Liaoning Province, China, in November 2014. The field LF had never been applied with any fertilizer for 27 years, while the field HF had been applied annually with fertilizer equaling to N 270 kg hm^-2. The soil samples were crushed gently into bits to pass through a 2 mm sieve and then air-dried to get ready for the incubation experiment. The ¹³C labeled maize leaf, stalk and root were cut into 2 cm sections, crushed to pass a 40 mesh sieve and mixed at a rate of 1% of the dried soil sample in weight separately with the prepared soil samples that had already been incubated for 7 days as pre-treatment. The mixtures were regulated in moisture content till 60% of field water holding capacity and then put into an incubator for incubation under a constant temperature (25℃) for 180 days. Each treatment had three replicates. During the period of incubation, the mixtures were sampled destructively on D1, D7, D28, D56 and D180 for analysis.【Result】Results show that (1) SOC content was found higher in the LF soils amended with maize leaf than in those amended with maize root and stalk after 28 days of incubation, while it was found higher too in the HF soils amended with maize throughout the whole incubation period; and after 180 days of incubation, the two groups of soils were quite similar in SOC content regardless of type of amendment; (2) the effects of the amendments of maize root, stalk and leaf on content of extraneous new C and residual rate of the substances varied sharply. The content of extraneous new C was found higher during the initial period of the incubation (before D28) in the low fertility soil than in the high fertility soil, while during the later half, an opposite trend was found. The residual rate of root residue was found lower than that of stalk or leaf residue in the low fertility soil during the later half period, while the residual rate of leaf was found lower than that of root or stalk residue in the high fertility soil. 【Conclusion】All the above-described findings indicate that the sequestration of extraneous new C was governed by its source and soil fertility level.