According to the original design of E’gan superlong highway tunnel, No. 1 inclined ventilation shaft, exhaust air releasing connection gallery and smoke releasing gallery of the tunnel are very steep, which results in construction difficulties, safety risks and potential delay of the construction schedule. In the paper, the difficulties of the original design are analyzed in terms of safety risks, construction difficulties, construction efficiency and construction schedule. The design of No. 1 inclined ventilation shaft of E’gan tunnel is optimized, i.e., the gradient of the inclined shaft is reduced and the connection between the connection galleries and the main tunnel is changed. The construction results show that the construction risks have been reduced, the construction efficiency has been improved, and the construction schedule has been met.