Supporting-free safe construction method for tunnel construction

The invention provides a supporting-free safe construction method for tunnel construction. The method includes: prefabricating a three-section reinforced concrete frame structure in a site outside a tunnel portal; utilizing a jack between a top back and the rear portion of a third section to push the reinforced concrete frame structure to the rear portion of the third section, and fixing the third section after the reinforced concrete frame structure reaches a designed position of the tunnel portal; utilizing a jack between a force transfer jack supporting pier and a rear acting force conduction supporting pier to push a first section and a second section to advance along with excavating of a tunnel, and building a tunnel structure section in a space between the second section and the third section. The first section of the reinforced concrete frame structure is utilized to replace a supporting structure in a conventional construction method, and the space between the second section and the third section is utilized to complete building of the tunnel structure, so that excavating while building effect is realized. Using of the supporting structure is not needed, so that engineering cost is lowered substantially; engineering operation links are closely connected, so that improving of construction progress is facilitated, and construction safety is guaranteed effectively.