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This study was about crop decomposition characteristic changes of corn and bean residues (with different water conditions and C/N ratios) decomposition in the fields of three land uses (vineyard, peach orchard, farmland), using nylon mesh bags method and thermogravimetry (TG), which can provide a scientific basis for the rational use of straw resources. The results showed that at the early stage of the decomposition (0~20d), the decomposition rate was more than 20% and the decomposition rate of bean straws was faster than that of corn straws. On 0~90d of the decomposition, they were relatively stable. Then the decomposition rates increased to 60%~70% at the end (300d). In TG-DTG curves, the mass loss of 200~300℃ stage（20%~30%） was caused by the corn straws during the decomposition (20~45d). At the end of decomposition, the 300~400℃ mass losses of bean straws were significantly higher than those of corn straws. The values of 600~700℃ in TG and DTG curves at the end of the decomposition (300d) were about 6%. The decomposition rates and percentages of fixed carbon and volatile matters were significantly different between fresh and dry treatments, corn residues and bean residues, and low C/N ratio and high C/N ratio treatments （P < 0.05). While, there were no obvious differences in three different land uses （P > 0.05). The decomposition rates and fixed carbon contents were significantly positively related to soil temperature and precipitation （P < 0.05), and volatile matters were negatively correlated with soil temperature and precipitation （P < 0.05). Corn and bean straws in soils could increase the carbon content. Type, C/N ratio and water condition of crop residues, and soil temperature and precipitation could affect the crop straw decomposition in the soil.