The invention discloses a tunnel design and construction method. Lateral walls of a tunnel are used as a supporting and protecting structure, and therefore a temporary supporting and protecting structure is replaced. A top plate in the tunnel is constructed in stages. A first stage of construction is used as a first tunnel support of a foundation pit, and therefore the first tunnel support is replaced. A tunnel middle wall is used as a temporary stand column of the support, and therefore the temporary stand column is replaced. A ground beam is used as a lowermost layer support of the foundation pit, and therefore the lowermost layer support of the foundation pit is replaced. A floor of a tradition open-cut tunnel is omitted. The ground beam is needed when lateral walls of the tunnel need to be subjected to force. The tunnel structure system constructed by the method is changed from single box single chamber or double chamber (single box and multi-chamber) closed box structure of a conventional tunnel to a door frame structure. The structural stress system is different from a tunnel built by traditional methods. Compared with a traditional tunnel construction method, material usageof the temporary supporting protecting structure and construction period are greatly saved.