A book returning system with a transverse moving mechanism comprises a plurality of book shelves at equal intervals. The book shelves use a book carrying tray in a matched mode. The book carrying tray is controlled by the transverse moving mechanism, a lifting mechanism, a rotary mechanism and a telescopic mechanism. The transverse moving mechanism comprises a rail, and roller wheels slide on the rail and comprise a driving wheel and a driven wheel. A motor is fixed to one side of a bottom plate and connected with a speed reducer, the speed reducer is connected with the driving wheel, and the driven wheel is further arranged on the other side of the bottom plate. The book returning system with the transverse moving mechanism has the beneficial effects of being accurately positioned to each row of each book shelf, achieving automatic positioning of each row of the whole book returning shelf, and enabling a user to conveniently find the book returning position.