Abstract: Chang 8 oil reservoir in S block of Ordos basin belongs to an ultra-low porosity and ultra-low permeability tight sandstone reservoir. Its development is not ideal, and the purposes of economic and effective exploitation have not been achieved in conventional single well with low well production, fast decline on the production and poor efficiency of water flooding. Therefore, a network fracturing technology in horizontal well was tested. According to the relevant data of S block, the difference coefficient of the horizontal principal stress of the target layer meets the ground stress condition of fracture network fracturing, which can produce fracture network. According to the requirements of fracture network fracturing,four horizontal well fracture network fracturing tests were completed in the research area. In the early stage after pressure, the average single well daily produced 40.9 m~3 of liquid and 23.3 t of oil., which obtained better development benefits.