Using the stable carbon isotope (δ¹³C) technique, an indoor incubation experiment was carried out to study distribution of fresh carbon in soil aggregate fractions of red soil (Ferrisols), yellowish red soil (Luvisol) and mountain meadow soil (Cambisols). To trace dynamics of fresh carbon in soil aggregates ¹³C-labelled rice straw was applied to the soils, which were then put under incubation at 25℃for 360 days. Results show that the quantity of the fresh carbon found in soil aggregates followed a decreasing order of 250 ~ 2 000 μm > 50 ~ 250 μm > <50 μm in all these soils, accounting for 56.8% ~ 59.6%, 25.9% ~ 28.7% and 11.7% ~ 17.3%, respectively, of the total applied into the soil, which further indicates that the added fresh carbon was mainly accumulated in large-sized soil aggregates.