The invention discloses a long-distance, heavy-load and parallel-axis type precision 2:1 transmission mechanism. The mechanism mainly comprises an input shaft, an output shaft, a flexible transmission part, a pre-tensioning pressing block, an end part fixing block, etc., wherein the input shaft is parallel to the output shaft and is connected with the output shaft through a flexible transmission part; two ends of the flexible transmission part are fixed to the output shaft; an intermediate part of the flexible transmission part is fixed to the input shaft; the input shaft in rotating can drive the flexible transmission part, and the flexible transmission part can synchronously pull the output shaft to rotate; as the input shaft and the output shaft of the whole mechanism are correspondingly connected with a driving end and a load end of an limited cornering device, the parallel 2-1 transmission of the driving end and the load under the long-distance and heavy-load condition can be achieved. The mechanism has the characteristics of being high in transmission accuracy, high in transmission rigidity, simple in structure, convenient to dismount and mount, low in processing cost, and easy to construct; the problem that the long-distance, heavy-load and parallel-axis type precision 2:1 transmission is hard to achieve by a traditional transmission mode can be solved.