The invention relates to the technical field of cutting of cold glass and discloses an online cutting and breaking-off mechanism for a glass door sheet. The online cutting and breaking-off mechanism comprises a rack, inflating press wheels and an ejector rod, wherein a cross beam is arranged on the rack; press wheel seats are arranged at two ends of the cross beam respectively; the inflating press wheels are arranged on the press wheel seats; a plurality of transfer rollers are horizontally and uniformly distributed below the cross beam and lower than the inflating press wheels; the ejector rod is located below the cross beam and arranged in a channel in the rack in a sleeving manner; a pulley is arranged at the lower end of the ejector rod, a cam matched with the pulley is arranged under the pulley, and an anvil is arranged at the upper end of the ejector rod. With the adoption of the scheme, compared with traditional manual breaking off, the online cutting and breaking-off mechanism has the advantages that the whole breaking-off process is performed on a production line formed by the transfer rollers, by means of the cam, the anvil performs upward ejection when a glass scratch is just located above the anvil, so that the production continuity is higher, meanwhile, scrap products caused by manual work are reduced, the labor cost is further saved, the production efficiency is improved, the structural design is reasonable, the operation is stable, and the online cutting and breaking-off mechanism is applicable to a large-scale glass door sheet cutting production workshop.