The invention discloses a method for winding and forming a rough yarn after a bobbiner is full of yarn, the method comprises the steps: calculating whether the length of a residual rough yarn accords with a preset value, controlling the bobbiner to spinning at a reduced speed; calculating whether the length of a yarn spun at a low speed accords with a preset value; the method also comprises: a flier motor, a drafter motor and a bobbin rotating body motor rotate at a low speed, a lower keel motor rotates at a high speed and the yarn is distributed at a thread pitch; if the yarn reaches a full-yarn forming upper part of the bobbin, then the flier motor stops, the drafter motor and the bobbin rotating body motor stop, the lower keel motor rotates at a high speed; if the yarn reaches the full-yarn forming top end of the bobbin, then the lower keel motor stops, keeps the position of the lower keel, the flier motor and the drafter motor and the bobbin rotating body motor rotate at a low speed, the yarn is winded on the full-yarn forming top end of the bobbin, all motors stop; the bobbin rotating body motor rotates reversely, the lower keel motor rotates and moves upward, breaks the yarn, completes the winding and forming of rough yarn after the bobbiner is full of yarn. According to the invention, the effect of rough yarn winding and forming after the bobbiner is full of yarn is ideal and free from falling.