The invention discloses a mechanical construction and fast location longitudinal connecting device for tunnel confined concrete arch supports. The longitudinal connecting device comprises a fixing component and a location guide connecting component which are fixed to the two sides of the arch support respectively and are coaxial, installation positions and directions of the fixing components and installation positions and directions of the location guide connecting components on the adjacent arch supports are consistent, the adjacent arch supports are connected through a longitudinal locating rod, one end of the longitudinal locating rod is connected with the fixing component of one arch support, and the other end of the longitudinal locating rod is connected with the location guide connecting component of the other arch support, so that the arch support being assembled and the arch support assembled already are located and fixed. The longitudinal connecting device is convenient and flexible to install and easy to operate, when the arch supports are located, only the two adjacent arch supports need to be in butt joint, the time for installing the arch supports is saved, and construction process is accelerated.