The physical characters of river-lake-delta sandstone in yanchang formation are controlled by deposition, burying, diagenesis and etc. in upper Triassic sandstone in ordos Basin. There are unique micro-pore texture and percolation mechanism in ultra-permeable reserior. Applying the technique of X-CT scanned image, the water driving oil test was made. By observing the CT scanned slice, the micro-percolation mechanism and the distribution law of water driving of rate (the highest water driving rate,62%; the lowest, 42%; average, 51.6%) were analysized, and micro-porosity character was evaluated quantitively. The essential reason that the great difference exists in parameters of starting pressure and water driving oil rate lies in low porosity, low permeability and double-porosity texture. The evident anisotropism is the main reason of low sweep efficiency and water displacement efficiency.