The invention discloses a fin-type field-effect transistor forming method, and the method comprises the steps: forming a stopping layer with an opening at the top of a first isolation layer, and exposing the top of a second isolation layer from the bottom of the opening; forming a protection layer on a side wall of the opening; forming a third isolation layer on the protection layer, wherein the opening is filled with the third isolation layer, and the material of the third isolation layer is different from the material of the protection layer; removing the stopping layer; removing a part of first and third isolation layers through back etching, wherein the etching rate of the third isolation layer is greater than the etching rate of the protection layer in the back etching technology; respectively forming gate electrodes on first isolation structures between the adjacent first fins and the adjacent second fins, wherein the gate electrodes are arranged across the first and second fins,and covers a part of top and side walls of the first and second fins; and forming a pseudo gate on a second isolation structure. The method improves the performance of the formed second isolation structure, and improves the electrical performance of the formed fin-type field-effect transistor.