The invention discloses a method and a device for winding and forming a rough yarn after a bobbiner is full of yarn. The method comprises that: if the length of a residual rough yarn is in accordance with a preset value, controlling the bobbiner to spinning at a reduced speed; if the length of a yarn spun at a low speed is in accordance with a preset value, controlling a flier motor, a drafter motor and a bobbin rotating body motor to rotate at a low speed, a lower keel motor to rotate at a high speed and the yarn to be distributed at a thread pitch; when the yarn reaches a full-yarn forming upper part of the bobbin, stopping the flier motor, the drafter motor and the bobbin rotating body motor and controlling the lower keel motor to rotate at a high speed; when the yarn reaches the full-yarn forming top end of the bobbin, stopping the lower keel motor, keeping the position of the lower keel, controlling the flier motor the drafter motor and the bobbin rotating body motor to rotate at a low speed, winding the yarn on the full-yarn forming top end of the bobbin and stopping all motors; and controlling the bobbin rotating body motor to rotate reversely, the lower keel motor to rotate and move upward, and breaking the yarn to complete the winding and forming of rough yarn after the bobbiner is full of yarn. The device comprises a draft detection part, a main control unit, a programmable controller, a variable speed controller, a filer, the lower keel and a detection device, wherein the lower keel is provided with bobbin rotating body and the bobbin; and the effect of rough yarn winding and forming after the bobbiner is full of yarn is ideal and free from falling.