The invention discloses a portal frame which comprises two slop plates and a plane plate, wherein the two ends of the plane plate are respectively connected with the slope plates in a rotary hinge mode, and two leaves of a hinge are respectively welded to one slope plate and the plane plate. Therefore, a stable threshold bidirectional ramp can be formed to enable vehicles to enter and exit safely when the plane plate is arranged on a threshold, arranging the two slope plates on the two sides of the plane plate and enabling one end part of each slope plate to be in contact with the ground. The invention aims at providing the portal frame which has the advantage of simple structure, easiness in processing and manufacturing, convenience, practicability and lower cost.