The invention discloses an initial access method and an initial access device of a terminal under a network slicing architecture. The initial access method comprises the steps of: sending a connection establishment request message carrying network slice selection information to a base station on a terminal in the terminal initial access process; receiving the connection establishment request message carrying the network slice selection information sent by the terminal on the base station; selecting a control plane entity providing a service for the terminal so as to establish connection for the terminal; receiving the connection establishment request message forwarded by the base station on the control plane entity; and establishing connection for the terminal which sends the connection establishment request message. By adopting the initial access method and the initial access device, the access of the terminal can be completed by means of the base station and the control plane entity and is no longer limited by a tight coupling relationship between the logical functions of the base station and the physical entity, a plurality of network slices can be deployed and supported simultaneously on the same set of physical entity, and the problem of insufficient flexibility of the existing network architecture can be solved.