Abstract: Based on the field survey and laboratory analysis, this paper studied the soil aggregate stability and soil organic carbon characteristics in  Quercus variabilis and Pinus tabulaeformis plantations in Beijing area. In the two plantations, the contents of soil macroaggregates decreased with soil depth. In P. tabulaeformis plantation, soil macroaggregates (>0.25 mm) occupied the majority, accounting for  71%-77% of the total; whereas in Q. variabilis plantation, no significant difference was observed in the contents of soil macroaggregates and microaggregates (≤0.25 mm), which accounted for 51%-58% and 42%-49%, respectively. Both the mean mass diameter and the geometrical mean mass diameter of the soil aggregates in P. tabulaeformis plantation were significantly higher than those in Q. variabilis plantation, and the fractal dimension (D) of the soil waterstable aggregates in P. tabulaeformis plantation was lower than that in Q. variabilis plantation, suggesting that P. tabulaeformis plantation was more favorable for the soil aggregate stability than Q. variabilis plantation. Also in the two plantations, the organic carbon content in soil waterstable aggregates decreased with soil depth. The organic carbon content in soil macroaggregates was significantly higher in P. tabulaeformis plantation (58%-83%) than in Q. variabilis plantation (49%-66%). It was suggested that in Beijing area, P. tabulaeformis plantation was more beneficial to the soil organic carbon protection, as compared with Q. variabilis plantation.