The invention discloses a central transfer case used for an automobile full-time four-wheel-drive system. The central transfer case comprises a driving shaft, a driven shaft, a driving gear, a driven gear, front one-way transmission ratchet wheels and rear one-way transmission ratchet wheels; a spline shaft sleeve is installed between the driving shaft and the driving gear; the driven gear can freely rotate on the driven shaft and is installed on the driven shaft in a slideable manner; outer rings of the front one-way transmission ratchet wheels and outer wheels of the rear one-way transmission ratchet wheels are both installed on the driven shaft through splines and locking nuts; inner rings of the ratchet wheels are positioned in the outer rings of the ratchet wheels through steps on the shaft and can freely rotate; a front one-way transmission ratchet wheel set and a rear one-way transmission ratchet wheel set are located on the two sides of the driven gear and are opposite in transmission direction; and the driving gear is engaged with the driven gear for transmission, and a shifting groove is formed in the driven gear. The central transfer case is simple in structure, low in cost, reliable in running, easy to operate, easy in matching, suitable for longitudinal layout rear drive vehicle types, high in applicability and large in transmission torque.