The utility model discloses an under constructing, wears by shield existing subway station envelope reinforcerment system, include: first reinforcement district for in the existing station outside, keeps away from newly -built station foundation pit another side envelope, hugs closely the stake of spouting soon of its construction and consolidates the district, the district is consolidated to the second, consolidates the district for the method of freezing that the subway envelope who hugs closely the sharing of existing station and newly -built station was under construction, should consolidate to distinguish and lean on existing station one side, the district is consolidated to the third, consolidates the district for the single RJP stake that the subway envelope who hugs closely the sharing of existing station and newly -built station was under construction, should consolidate and distinguish by newly -built station one side, dive precipitation well is established inside newly -built station foundation pit, the usefulness of double as confined level peephole is established outside newly -built station foundation pit to reserve pressure -bearing water precipitation well. The utility model discloses can effectively improve next -door neighbour's envelope soil body from stability and bearing capacity, reduce the shield and construct into the hole, gush swelling sand risk when arriving at a station, reduce the operation influence of existing station.