Abstract:【Objective】The objective of this study was to assess the effect of land-use changes on the composition and stability of soil organic matter (SOM). 【Method】Based on a 29 years long-term experiment in typical Mollisol region, we investigated the contents of labile fractions of SOM in depths of 0～10、10～20、20～40、40～60、60～80 and 80～100 cm. Furthermore, Fourier transform infra-red and solid-state 13C nuclear magnetic resonance spectroscopies were applied to estimate the differences in functional C groups of SOM under different land uses. The land-use types included cultivated land (CL), restored grassland (GL)and artificial spruce forest land (FL). 【Result】The contents of soil labile organic C fractions (i.e. microbial biomass C, dissolved organic C, light fraction organic C and readily oxidizable organic C)were higher in GL and FL than in CL at all soil depths, and followed the order of GL> FL >CL. With the increase of soil depth, the aliphatic C, OCH3 and O-alkyl C groups of SOM gradually decreased, while the aromatic C and carboxyl C gradually increased. This indicated that the stability of SOM increased with soil depth. The proportion of OCH3 and O-alkyl C groups from plant residues were highest in the GL across all depth, followed by FL, and lowest in the CL. The SOM of CL had higher proportion of aromatic C and carboxyl C groups than that of GL and FL. This resulted a higher humification degree of SOM in CL. 【Conclusion】Our results suggest that land use changes modify the chemical composition of SOM both in the topsoil and subsoil. Vegetation restoration could increase labile components of SOM. In contrast, long-term cultivation prompted the accumulation of recalcitrant fractions in SOM.