The multi-scale complex fracture networks are formed by volume fracturing in tight oil reservoirs. At the same time，the uncertainty of reservoir parameters is significantly enhanced due to the strong heterogeneity. It is very important to accurately characterize fractures and reduce the uncertainty of reservoir parameters for building an accurate reservoir numerical simulation model. Therefore，a numerical simulation model for CO2 huff-n-puff in tight oil reservoirs was constructed according to the embedded discrete fracture model（EDFM）. By doing this，the multi-scale complex fracture network of tight oil reservoirs after fracturing was effectively characterized. With the ensemble Kalman filter（EnKF）method，the intelligent historical matching was carried out for CO2 huff-n-puff production data of tight oil reservoirs，and the physical properties and fracture parameters of reservoirs were estimated，which reduced the uncertainty of model parameters. The results show that the EDFM-based simulation model for tight oil reservoirs can accurately characterize multi-scale complex fracture networks and is suitable for treating complex fractures in tight oil reservoirs after fracturing. Pseudo-and real-vertices exist in the production curve calculated by the multi-scale medium model after effective medium treatment，which is consistent with the actual CO2 huff-n-puff production law of tight oil reservoirs. Upon repeated iterative matching with the EnKF intelligent history matching method，the convergence of the ensemble parameter curve of the initially realized multi-scale fractured medium model is enhanced，and the simulated production and production history of two horizontal wells，i.e.，Well J1 and Well J2，are well matched.