Soil physiochemical properties and stable carbon and nitrogen isotopes of grazing and fencing for 3 and 5 years were analyzed in the Xilamuren degraded desert steppe of the central-western Inner Mongolia. The results showed that: 1) Fencing increased the contents of soil organic carbon, total carbon and soil moisture and soil carbon-nitrogen ratio (C/N)(P < 0.05) compared to free grazing. Soil bulk density and total nitrogen content were reduced(P < 0.05), while the total nitrogen content of soil tended to increase with fencing years. 2) The values of δ¹³C and δ¹⁵N of enclosing treatments decreased with fencing years(P < 0.05). 3) Soil organic carbon content was negatively significantly correlated with its δ¹³C value (P < 0.05), while the total nitrogen content was positively significantly correlated with its δ¹⁵N value(P < 0.01). In general, enclosure is beneficial to promote soil organic carbon accumulation, retard soil nitrogen cycle, and improve soil properties in degraded desert steppe.