The invention discloses a bearing and driving mechanism for a sliding door of an urban rail vehicle. The bearing and driving mechanism comprises a slideway component, a driving screw rod, a screw rod driving component, a driving support, a plurality of bearing wheels, a left-door-leaf bearing support, a right-door-leaf bearing support, drag chain supports and drag chains. The screw rod driving component is arranged on one side of the driving screw rod, and a manual unlocking device is arranged on the other side of the driving screw rod. The slideway component is mounted below the driving support. The bearing wheels are arranged in the slideway component. The left-door-leaf bearing support and the right-door-leaf bearing support are connected with one ends of the corresponding drag chains respectively, and the other ends of the drag chains are fixed on the drag chain supports respectively. The drag chain supports are fixed on the driving support. A front bearing piece, a middle bearing piece and a rear bearing piece are sleeved on the driving screw rod. Bearing capability of the bearing and driving mechanism is improved, abrasion of higher pair connecting mechanisms is reduced, service life of the driving screw rod is guaranteed, product quality is stabilized, product competiveness is improved, and the bearing and driving mechanism has good application prospect.