Taking the large deformation of a highway tunnel with weak rocks as the engineering background, a three-bench seven-step excavation inverted arch following construction method has thus been proposed by means of an on-site investigation, a numerical simulation and an on-site monitoring. Two numerical models of a three-bench, seven-step excavation method are established by using Midas GTS, followed by an analysis of the large deformation of the tunnel in combination with the geological exploration and laboratory test data, with the simulation results of the new construction method compared with that of the monitoring data. The research results show that the inverted arch following technology in the proposed construction method plays an importart role in the deformation control, which can not only effectively control the large deformation found in tunnel construction, but also shorten the construction period, thus improving the construction efficiency and saving the project cost as well.