The road between Ponsanooth and Treluswell closed as cutting a tree down that is dangerous and could fall onto power lines.
Traffic is queuing after Cormac blocked the road to remove the tree which has been damaged by the recent storms.
Cornwall was pummelled over the weekend by Storms Eunice and Franklin with hundreds of trees falling or being seriously damaged.
Many people in the coubnty are still without power after many power lines were brought down by falling trees.
It is not known how long the tree removal will take, but the council is being forced to remove many trees before they fall.