The utility model relates to an immersed tube tunnel technology field, concretely relates to M waterstop that appears, including being used for the first connecting portion is connected with final joint body structure, and be used for pushing away the second connecting portion that the trabecula is connected with pushing up, be the pars contractilis between first connecting portion and the secondconnecting portion, this pars contractilis is flexible material, and when the top pushed away little back and pushes away, the pars contractilis was the M shape, first connecting portion, second connecting portion and pars contractilis formula structure as an organic whole on body structure who fixes M waterstop that appears at final joint respectively through connecting portion and top push awaythe trabecula, makes M waterstop that appears push away trabecula cavity structure with the top of inboard and blocks with the sea water in the outside to reach the stagnant water purpose, prevent thesea water get into reach the summit push away trabecula and final joint's cavity structure in, guarantee final joint's smooth installation and construction safety.