Abstract: It′ s very often to encounter water leakage at the portal of urban metro tunnel. An investigation is con? ducted aiming at the water leakage diseases at the portal of certain urban operating shield tunnel, and the causes are analyzed. The results show that the main causes of water leakage include disturbance of external soil mass, watercontaining cavity due to non-impacted secondary grouting, and rigid and flexible contact at portal. The key technical points and difficulties are described based on two typical cases of water leakage remediation at portal of operating metro tunnel, and the principles and recommendations for treatment of water leakage at tunnel portal are proposed.