Abstract: Combining field sampling and laboratory experiments, we conducted an in-depth analysis on variation of soil particle size of farmland topsoils in a selected study area and the influencing factors. Results show that the main mechanical composition of farmland topsoils were composed of silt and sand. The soils presented a light texture in which clay and sand contents exhibited the weak to moderate variation. For individual land use types, the clay content in the fruit woodland was the highest, while the mixed crop land for the lowest. The silt content in the mixed crop land was the highest, while cotton fields for the lowest. The sand content in the cotton fields was the highest, while the grain crop field for the lowest. For cotton cropping fields, the clay content was shown the highest in the 15-year continuous cropping field, while the lowest in the 20-year continuous cropping field. The silt content was shown the highest in the 15-year continuous cropping field, while the lowest in the 25-year continuous cropping field. The sand content was shown the highest in the 25-year continuous cropping field, while the lowest in the 15-years continuous cropping field. Generally speaking, in the junction of the rivers of Ugan, Kuqa and Tarim with strong alluvial matter exchange, the clay and silt contents were relatively high, while the sand content was low. In the oasis surrounding areas, the clay and silt contents gradually decreased, while the sand content increased. The deterministic factors such as properties of soil parental materials, topography, meteorology and climate were the main factors that control the variation of soil particle size of farmland topsoils in the studied area, while the random factors like human activities for agricultural production intensified the structural changes in the soil particle size of farmland topsoils.