“Pisha” or soft sandstone, distributed extensively in the region striding over Shanxi Province, Shaanxi Province and Inner Mongolia Autonomous Region, is a kind of sandstone, highly erodible and unfit for vegetation growth. It is also one of the major sources of coarse sediment in the Yellow River. As it contains abundant montmorillonite, this kind of soft sandstone is quite high in water holding capacity. An indoor simulation experiment was carried out on feasibility of using weathered soft sandstone to ameliorate the local soils (Aeolian sandy soil and sandy loess, rather coarse in soil texture) in water holding capacity. The experiment used 3 types of soft sandstones different in color (red, gray and white) in amendment in the ratio of 1:9, 3:7 and 1:1(by weight) separately, to determine effects of the amendment on water retention curve and evaporation process of the local soils. The experiment was conducted in the State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau, Institute of Water and Soil Conservation, Chinese Acdemy of Sciences. Three kinds of soft sandstones (Red, Grey, White sandstone) were mixed with aeolian sandy soil and sandy loess, separately, in line with the designed ratios, 1:9, 3:7 and 1:1 (by weight of air-dried soil, m_{soft sandstone} /m_soil), and each had 3 replicates. Original soils were also tested as control. The experiment proceeded under natural conditions. A centrifuger was used to determine soil water retention curve at 12 set rotation rates and the RETC software and van Genuchten model was used to fit the soil water retention curve, and soil evaporation processes were determined through in-lab simulation, using a hard plastic beaker with punched bottom. Before packing soil into the beaker a piece of filter paper was placed on the bottom to prevent the soil from leaking. The beaker was put into a pan with water to wet the soil in a self-suction way through the holes in the bottom for 12 h till the surface of the soil was wet, and then the beaker was put aside for 4 h to drain out gravity water. During the process, the soil was mulched with foam to prevent the water from evaporation loss. The saturated soil column was drained for 4 h to make sure the gravity water out. Weighting method was used to determine evaporation rate. Soil bulk density of the soil in each treatment was controlled as listed in Table 2. Results of the experiment show that (1) weathered soft sandstone was higher than the two local soils in water-holding capacity and amendment of the former improved the latters in water-holding capacity and reduced their water losing rate. White soft sandstone reduced saturated water content of the sandy loess;(2) Soft sandstone, when low in proportion (1:9), improved water supply capacity of the two local soils, but did not have much effect increasing water suction of the soils when specific water capacity of the two soils reached the 10^-2 level, which indicates that the effect of soft sandstone improving the local soils in water holding capacity is not significant, when they are low in suction; (3) Soft sandstone decreased standard evaporation rate of the sandy loess and lowered standard evaporation in the aeolian sand soil, too, but only at the initial stage of the evaporation, and affected reversely in the middle and late periods. The higher the proportion of soft sandstone, the higher the standard evaporation in the Aeolian sand soil. In sandy loess proportion of soft sandstone was not an important factor affecting standard evaporation. The standard evaporation from the mixture of soft sandstone and sandy loess was quite close to that from soft sandstone; (4) In the aeolian sand soil, though addition of red, grey and white soft sandstone increased water loss through evaporation by 11.59%, 10.14% and 0.01%, respectively, it multiplied the eventual moisture content by 4, 2.33 and 1.33 times, respectively, while in the sandy loess, the addition decreased water loss through evaporation by 13.33%, 13.33% and 29.52% and the eventual moisture content, too, by 45.83%, 54.17%, and 66.67%, respectively. The findings may serve as a certain theoretical basis for and a possible technical approach to soil and water conservation and ecological restoration in this soft sandstone region.