Abstract: Fractures of sandstone reservoir are chiefly horizontal fractures and dipping fractures of low angle in Yangjiaba Oilfield. Fracture density is obviously influenced by lithology, thickness and structural location. Fracture density in siltstone is higher than other lithology. There is higher fracture density in thin sand than thick sand. Fracture formation is controlled by boarder fault. The result shows that Fracture distribution density is high nearby boarder fault and on the axis of structural nose than the alar part. Combined with the dynamic documents, influences of fractures on development effect are analyzed. Because of fractures, oil layer production is high, but edge and injection water invade seriously , escalating rate of water cut is rapid and recovery factor is low. As a result, fracture developed in thin sand, and serious water flood, the potential tapping is still in thick oil layers for the later stage of Yangjiaba oilfield development.