The invention relates to an apparatus for replacing a bobbin on a ring spinning frame. The invention aims at providing a doffing trolley traveling and sliding device which has high efficiency in drawn work, and can prevent damage to apparatus. The doffing trolley traveling and sliding device comprises upper guide rollers, an upper guide rail, a traveling driving motor, a gear wheel and a gear rack. The upper guide rollers are horizontally mounted at one side of the ring spinning frame through a rail support. The gear rack is fixedly mounted at the lower part of the upper guide rails. Two guide roller fixing plates are mounted at one side of a doffing trolley near the ring spinning frame. Each guide roller fixing plate is mounted thereon with two upper guide rollers. The upper guide rollers are arranged above and matched with the upper guide rail. A shaft hole is arranged on one guide roller fixing plate. The traveling driving motor is mounted in the doffing trolley. An output shaft of the traveling driving motor passes through the shaft hole to connect with the gear wheel. The gear wheel is arranged under and engaged with the gear rack.