Block Fan142 in Zhenglizhuang Oilfield is a typical low porosity，extra-low permeability beach-bar sand reservoir with the rapid production decline and low recovery during the elastic development period. In order to study the feasibility of CO2 miscible flooding in the extra-low permeability beach-bar sand reservoirs，a pilot test was carried out in Well Group F142-7-X4 of the Block Fan142. The results show that CO2 has a good effect on reducing viscosity and swelling formation oil，which can dramatically improve oil recovery. By using numerical simulation，the formation pressure may be restored through the optimization design of CO2 flooding. The higher recovery and economic benefit of the well group may be obtained at the conditions of the inverted seven-point pattern，the cyclic injection and production，and maintaining formation pressure at 1.3MMP. The field test results show that CO2 has a good injection capacity and the formation pressure of the well group is significantly restored. A good stimulation performance is achieved. The oil exchange rate by gas injection of the well group at the miscible phase is 0.44 t/t and oil recovery factor of well group is increased by 6.2%. The CO2 miscible flooding is an effective means to improve the recovery of the extra-low permeability reservoirs.