【Objective】The semiarid region of Weibei is identified as one of the best “eugenic” apple-producing areas in China, owing to its unique eco-environmental conditions. Since the 1980, Weibei has adjusted its agricultural structure by converting large areas of farmland into apple orchard, in order to improve local ecological landscape and economy. But this change inland-use and implementation of a series of unscientific orchard managements (e.g., inappropriately increasing the application of inorganic fertilizers and pesticides) has led to soil quality degradation, such as declining soil micro-ecosystem biodiversity, soil nutrient imbalance, and their subsequent impacts on yield and quality of the fruit getting more and more significant with increasing age of the apple orchards. Soil aggregates and their stability influence a wide range of soil properties, including carbon stabilization, soil porosity, water infiltration, bulk density, water erosion resistance, etc. Aggregate stability is an issue that has been a focus of increasing attention in recent years as one of the soil properties that can serve as an important indicator of soil quality. So it is necessary to study status and evolution of soil aggregates as affected by changes in land use and management practice and ongoing cultivation as apple orchard in an attempt to provide a scientific basis for maintaining sustainable development of the apply industry and the ecology in the region.【Method】In this study, two apple orchards different in age (10a, juvenile and 21a, over-mature) and a tract of farmland nearby were selected in the semiarid loess region of Weibei, Bin country, Shaanxi, China as objects for investigation of soil aggregates in the 0~40 cm soil layer. Soil samples collected from the sampling lots were analyzed for fractionation of soil aggregates with the dry-sieving and wet-sieving methods, and so for soil basic properties, and soil aggregate stability and correlation between the two.【Result】Results show that the fraction of <0.25 mm micro-aggregates dominated in the soil layers of the apple orchards and farmland (CK).The topsoil (0~20 cm) in the apple orchards displayed a pronounced aggregation trend with age, which was embodied in significant increase in content of >0.25 mm soil aggregates (DSAC_0.25), mean weight diameter (MWD) and geometric mean diameter (GMD) and decrease in fractal dimension (D), content of 10~0.25 mm and 5~1 mm valuable aggregates and coefficient of aggregate (K_CTP).The composition of water-stable soil aggregates in the soil of Weibei, about 60% was<0.25 mm soil micro-aggregate. In terms MWD, GMD and WSAC_0.25of water-stablesoil aggregates in the 0~30 cm soil layer, an decreasing order of CK >Orchard of 10a >Orchard of 21a was found, and the trend was getting more and more obvious with increasing orchard age. Soil water stable aggregates, soil structure, erosion resistance and fertility retention ability in the 0~30 cm soil layer of apple orchards decreased with increasing orchard age. WSAC_0.25 was significantly lower than DSAC_0.25. Destruction rate of >0.25 mm soil aggregates (PAD_0.25) also significantly increased with increasing orchard age, and the increase declined in extent with soil depth. Correlation analysis shows that soil total organic carbon (TOC) , and particulate organic carbon (POC) was closely related to various indices of mechanically-stable soil aggregates, while soil CaCO₃ content and clay content were significantly related to a number of indexes of water-stable soil aggregates, and PAD_0.25 to soil physical and chemical properties.【Conclusion】Orchard plantation apparently increases the content of mechanically-stable soil macro-aggregate content in the 0~20 cm, soil aggregation level, and hence its resistance to wind erosion, but significantly reduces agronomical quality and stability of soil aggregates. The significant degradation of agronomical quality of soil aggregates in apple orchards is directly related to the decrease in soil organic matter and CaCO₃ content in the soil. It is, therefore, recommended that in this semiarid region, more input of easy-to-decompose organic manure, and appropriate soil management measures be adopted to improve stability of the soil in structure, solve the problem of soil degradation in orchards, and promote sustainable development of the apple industry in the region.