The invention discloses an infusion bag extruding device for medicine dispensing by a penicillin bottle and a medicine dispensing method. The extruding device comprises a substrate, wherein an infusion bag and a mounting station of the penicillin bottle are arranged on the substrate; a lifting part is arranged above the mounting station of the infusion bag and comprises a support; a cam and at least one bull eye bearing arranged on the cam are arranged on the support; the cam is connected with a rotating motor; the height of the support is adjusted to be matched with that of the infusion bag; when the rotating motor drives all the bull eye bearings on the cam to rotate along the circumference, the bull eye bearings are in contact with the infusion bag and can extrude the infusion bag. The extruding device is simple in structure and convenient in use; liquid in the infusion bag and the penicillin bottle can be directly injected or flow out without adopting a transit container to communicate the infusion bag with the penicillin bottle, the structure is optimized and interactive infection is avoided. Compared with a manual extrusion mode of the infusion bag, the medicine dispensing method has the advantages that the infusion bag can be automatically extruded or release the pressure, the medicine dispensing efficiency is improved, and the medicine dispensing time is saved.