One of the key technique problems of reconstructing underground gas storage (UGS) using low permeability depleted gas reservoir is the stability of gas-water interface (GWC). To analyze the stable migration of GWC in gas storage reconstructed from low permeability gas reservoir using CO₂ as part of the cushion gas during capacity expansion by gas injection and seasonal peak shaving of UGS, a dual-porosity numerical model was established based on the characteristics of low permeability micro fractured reservoir. Taking the reservoirs of Wen-23 gas storage reconstructed, the Zhongyuan Oilfield, as research objects, the effects of CO₂ injection method on capacity expansion of UGS and migration behavior of GWC when peak shaving were simulated and discussed. The results showed that the method of continuously CO₂ injection increased capacity expansion speed but reduced the stability of GWC and reservoir pressure field during capacity expansion. The method of CO₂ injection at intervals reduced the rate of capacity expansion by 4.8% after 4 cycles, but could ensure stable migration of GWC and the stable of reservoir pressure field. Besides, the stability of GWC and reservoir pressure field were better ensured by the transformation between dissolved state and supercritical CO₂ during seasonal peak shaving of USG, and the utilization of reservoir space were increased, simultaneously.