Nonlinear bipolar resistive switching (BRS) of Al/NiO/ITO without forming is demonstrated in this paper. Compared with the linear BRS needing forming, the forming-free nonlinear BRS can be operated using a smaller current about two orders at a smaller switching voltage in the same device. Different from the Joule heating mechanism of the linear BRS behavior after forming, the conduction of the nonlinear BRS is dominated by oxygen vacancy drift induced by electric field across the interface between metal Al, NiO film, and conducting ITO, in which Al/NiO interfacial layer and ITO act as a dual-oxygen reservoir. Furthermore, the doping of Li into NiO layer improves switching properties such as the ON/OFF ratio and reproducibility due to the increase of oxygen vacancy. The results imply that forming-free nonlinear BRS of binary oxides caused by interface layer is feasible in similar dual-oxygen reservoir structure.