One of The important subjects about Zagros mountain range is the lack of coordination between its drainages and geologic structure. This subject on Zayandehrood drainage system has become one of the most challenging discussions and three different theories have been proposd . To remove these disagreements and to achieve a general conclusion, this basin and two basins of Azna and Kakolestan at a distance of 62 and 85 km form its north east limit were studied exactly in library and in the field. With referrer to different evidence obtained from the condition of river terraces, lake sediments and fossils, cirques and glacial sediments and active tectonic, it may be concluded that during Pliocene the Zagros drainages have been flowing toward Persian Gulf, but this drainages have been trapped because of the activity of Main Recent Fault at late this period or Early Pleistocene and formed some lakes. Later as the result of some processes that most of them have been of tectonic origin, the bed of these lakes were disintegrated and the water stream was flowed in Kakolestan and Azna’s basins at the previous direction and in Zayandehrood basin at the revers direction.