The invention relates to an emergency separating device for liquid transmission, which comprises an upper valve body, a lower valve body and a locking assembly, wherein a clamping plate seat of the locking assembly is arranged at the side of the upper valve body; valve core rotating rods of the upper valve body and the lower valve body are arranged at the front surfaces of the upper valve body andthe lower valve body; the end parts of the valve core rotating rods are provided with transmission gears; a transmission block driven by an oil cylinder is arranged between the two transmission gears; the transmission block is provided with an upper gear rack and a lower gear rack which are matched with the two transmission gears; a locking rod is provided with a lengthened push rod; the oil cylinder is perpendicular to the lengthened push rod of the locking rod; mutually meshed synchronous gears are installed on an articulated shaft between a front clamping plate and the clamping plate seatand between a rear clamping plate and the clamping plate seat. The locking rod is pushed by the oil cylinder, and the clamping plates are pushed so that the front clamping plate and the rear clampingplate are forcibly opened synchronously from the valve body; the two clamping plates rotate to the outside synchronously under the action of a tension spring by the rotation of the synchronous gears,and the two valve bodies are thoroughly separated, in a safe and reliable way; in addition, both the opening and the closing of valves are finished by the oil cylinder, thereby having convenient installation debugging, low labor intensity and high working efficiency.