The present application provides a preparation method for a porous carbon material, comprising the following steps: (1) soaking cellulose fibers in a 5 wt% to 40 wt% zinc chloride solution for 30-60 mins to partially dissolve the surface of the cellulose fibers; (2) curing the fibers in deionized water for a while, and then placing same into a drying device for drying; and (3) performing carbonization using argon as a protective atmosphere. The present application firstly proposes using a simple and feasible new method, namely, a selective surface dissolution method, to pre-treat cellulose fibers and then carbonizing same at a high temperature, obtains optimal process parameters by investigating the influence of each process parameter on pore structure and electrochemical properties, and prepares a porous activated carbon material having a large specific surface area and having rich pore structures. The porous activated carbon material is prepared into a super capacitor as an independent electrode material (without filling a conductive agent and a binder). The super capacitor has a specific capacitance up to 488 F/g, much higher than that of the existing super capacitor of the same type, and thus has a wide application prospect.