Abstract In order to study the changes in two‐phase flow parameters after pipeline damage and the impact of gas injection on water leakage from damaged pipelines, experimental and simulation studies were conducted on the damaged pipelines. The main objective is to compare the void fraction in intact and damaged states and to investigate the factors influencing and variations in gas–liquid leakage flow rates. The results show that increasing the liquid superficial velocity can reduce the difference in void fraction distribution caused by different damage directions. The leakage flow rate is affected by the direction of damage and the superficial velocity of the respective phase. It has been discovered that gas injection in the pipeline can make it easier to find small‐area pipeline damage. The change rate of the volume void fraction shows different changes with the increase in gas proportion in different directions; the shape of the bubble has no bearing on this change.