Soluble organic carbon (SOC) in plant residues extracted by water or different extractants is an active component, and has important roles in carbon and nitrogen biogeochemical process in soil ecosystem. Reestablishing the vegetation on the Loess Plateau is changing the types and amounts of the plant residues into soil ecosystem. Therefore, our objective was to evaluate the contents and biodegradation of SOC of residues of different species from this region. Six species of plant residues were sampled from Shenmu, North of the Loess Plateau, and the contents of SOC in two sizes residues (2 mm and 1 cm length) was extracted with two extractants (distilled water and 0.01 mol x L(-1) CaCl2). And a 7-day incubation experiment (25 degrees C) was conducted to compare the biodegradability of SOC of the different plant residues. The contents of SOC in the different plant species ranged from 4.21 g x kg(-1) to 76.25 g x kg(-1), and the rates of SOC to total carbon (SOC/TC) of the plant residues were in range of 0.99% and 19.84%. The order about the average content of SOC and SOC/TC of the different plant species was trees > shrubs > grasses. After 7-day of incubation, rates of biodegradation of SOC in different plant residues ranged from 34. 7% to 75. 1% (averaged 56.3%). The proportion of complex structure SOC increased significantly in solution at the end of incubation, indicated the rapid biodegradation of labile composition in the residues.