The invention discloses a quick unfoldable prestressed steel bridge which comprises a bridge deck, transverse separating rods and two or more unfoldable prestressed steel frames. The bridge deck is laid on the transverse separating rods at the top, the unfoldable prestressed steel frames are positioned below the bridge deck, each unfoldable prestressed steel frame comprises a scissor-fork-type rod and a steel rope, two end heads and the middle of each scissor-fork-type rod are connected with the transverse separating rods, each steel rope is a prestressed steel rope, and by adopting an in-profile rope laying mode, pulling force borne by lower chord rods is replaced after prestress is applied, so that material performance is brought into full play; the unfoldable prestressed steel bridge is fixed on the ground through supports, constraint capability of the supports is improved, and anchor rods are arranged at the supports at two ends. The quick unfoldable prestressed steel bridge is short in erection time and convenient to carry, and can be used as a temporary bridge in the process of urban road reconstruction, during emergency rescue and disaster relief and for military use.