At present, most multiarch tunnels at home and abroad adopt the construction method of middle guiding tunnel, but the research on the construction without middle drift is relatively few. As for no drift construction, few actual engineering experience and nearly no deep and systematic research on the advantages, disadvantages and application can be found. Shangchangping tunnel is a separated tunnel transiting to multiarch tunnel. Due to its connection and transition with the bridge, the design of the middle partition wall varies in thickness, which adopts the composite thin straight middle wall with novel structural design. With the requirement of no change in design and finish 504 m within 4 months, in order to implement the challenging design scheme, the problem of pouring the second lining of the middle wall is successfully solved by using vertical steel shotcrete structure which is poured between the left and right holes as the structural part of the middle partition wall. At the same time, the problems of leakage prevention and cost control are also resolved, and the unprecedented construction technology is introduced to increase the new process type, providing the new case of no middle guide tunnel construction for Ⅳ surrounding rock tunnel projects.