The invention discloses an excavation construction method for a super large cross section tunnel of bias shallow buried weak surrounding rock. A temporary median lamella wall is adopted to divide a tunnel face into a left part and a right part; and the left part and the right part are excavated simultaneously through a three-bench-five-step method. According to the three-bench-five-step excavation method of the median lamella, when the geological condition changes, construction processes can be converted flexible and timely, the construction method is adjusted, and the construction period is shortened. The excavation method is simple in process and reliable in excavation, excavation of the super large cross section tunnel of the bias shallow buried weak surrounding rock is provided an important guarantee, the failure rate is low, and the project profitability is enhanced. A locking anchor pipe replaces a traditional locking anchor rod, the stability of the structure is also improved, meanwhile, steel pipes are adopted to fix steel frames, so that the steel frames form a whole through the connected steel pipes, the system bearing load is improved, the fixing effect of the steel frames is better, and control of tunnel deformation is very favorable.