Abstract: With the application of close-spaced volume fracturing technology in Qingcheng oilfield in Ordos Basin, the proportion of fracture-driven interactions wells in shale oil reservoirs has increased, and thus, optimization of horizontal well spacing in shale oil has become a major concern. In order to develop Chang 7 shale oil reservoir in Qingcheng oilfield in Ordos Basin as expected, under the guidance of indoor theoretical calculations and numerical simulation studies, the field development practice with various well spacings was carried out, and its 3-year production data were statistically analyzed. Using such parameters as ultimate recoverable reserves of single well and 100 m layer oil production capacity of single well, the optimal well spacing for reasonable development of the shale oil horizontal well is determined. Based on the research results with combination of bottom hole micro-seismic method, rate transient analysis method, and well test interpretation method, it is determined that the effective fracture half-length after fracturing should be no more than 150 m, and the effective matrix seepage range is 45 m. Therefore, the reasonable well spacing is finalized to be 400 m according to the fracture network matching theory. On the basis of numerical simulation of the reservoir, and taking the oil production of a single well and the cumulative oil production of the block into consideration, the well spacing of the studied block is preferred to be 400~500 m. Based on the actual production data analysis of horizontal wells with varying well spacings on site, the assessed ultimate recoverable reserves of a single well with 400 m well spacing is 9.6% higher than that with 300 m spacing, and the block recovery rate is 20.8% higher than that with 500 m spacing. Thus, it is considered that 400 m spacing is more suitable for the development of horizontal wells of interbedding shale oil in Qingcheng Oilfield.