通过室内试验，对大粒径（2.0 ～ 3.2 mm）、中粒径（1.0 ～ 2.0 mm）和小粒径（0.5 ～ 1 mm）3 种粒径保水剂的吸水特性进行了测定，同时对施加不同粒径保水剂前后的沙质土壤的理化性质进行对比分析。结果表明：①保水剂的吸水倍率与其粒径大小呈负相关关系；②保水剂对土壤水分蒸发有明显的抑制效应，能显著提高土壤的水分含量；③保水剂会使土壤 pH 和电导率升高，降低土壤渗透性，土壤中液相比例增加的同时气相比例会相应减少。综合考虑 3 种不 同粒径保水剂对土壤理化性质的影响，中粒径保水剂改善效果最好，在施用量为 0.1% 时，对土壤的改良效果最为明显，亦不会产生明显副作用。 In this paper, the effects of super absorbent polymer ( SAP) on soil physical and chemical properties and the relationships among water absorbent capacity of SAP with three different granularities ( 2.0-3.2 mm, 1.0-2.0 mm and 0.5-1.0 mm) were studied in laboratory. The results showed that there was a negative correlation between water absorbent rate and SAP granularity. Soil moisture content could be significantly increased and soil evaporation could be restricted after applying SAP. Soil pH value and electrical conductivity could be increased after applying SAP, the proportion of liquid phase in soil could be increased, but that of gas phase decreased, and soil permeability could also be decreased. In general, the improving effects of SAP with medium granularity on soil physical and chemical properties, such as soil water content, pH value, total porosity, permeability and electrical conductivity, were the highest, especially when the proportion of applied SAP was 0.1%.