In long distance shield tunneling of open-type TBM, the outer sealing ring may cause breakage and shedding due to frequently vibration. In order to solve the problem, taking the open TBM with ?8. 5 m in a domestic water diversion project as an example, combined with the construction site conditions, the feasibility and economy of three treatment schemes are made a contrastive analysis. An innovative solution is proposed and a new maintenance technology for outer sealing ring of TBM main bearing is developed. If the main bearing seal is undamaged, the bolt connection mode of the original design can be changed. The new gear ring is installed in four sections and welded to the connecting seat and without removing the cutter head. If the main bearing seal is undamaged, the bolt connection mode of the original design can be changed. The new gear ring is installed in four sections and welded to the connezcting seat and without removing the cutter head. Compared with the regular treatment which is required to dismantle the cutter head and excavate and expand the hole to install the full circle, the new scheme is much easier and with reduction of the workload by more than 85% on the original basis, shortening the construction time from four months to half a month, which saved a lot of valuable time for the construction schedule and greatly reduced the economic costs.