[Objective] To explore the effect of water-physical properties of feldspathic sandstone modified by a kind of hydraulic polyurethane (W-OH), and to provide the theoretical guidances for high slope protection of feldspathic sandstone.[Methods] By tasting indices such as the water stability and erosion resistance of the feldspathic sandstone modified by the W-OH, the modified mechanism was analyzed.[Results] It was indicated that the water stability and erosion resistance of the aggregates in modified feldspathic sandstone were obviously improved with the decrease of the particle size of the aggregates, the K was increase. The addition of W-OH significantly reduced the sediment yield and sediment yield on the slope.[Conclusion] Soil and water loss from the slopes decreased greatly and the slope stability was enhanced by cementing sands which a solidified layer on the surface of the feldspathic sandstone was formed.