We report on the strategy of controlling the morphology of CoO/reduced graphene oxide (rGO) composites through regulating the assembly of CoO nanoparticles in the CoO/rGO composites by using oleic acid (OA). With increasing of OA amount, the morphologies and structures of CoO/rGO composites display special changes. The OA was found to influence the assembly of CoO nanoparticles on the surface of rGO sheets. As the content of OA is 1 mL, the obtained CoO/rGO composites (S-1) shows 3-D network CoO anchored with rGO sheets structure. This 3-D CoO microstructure is composed of intertwined nanowires which assembled by tiny CoO nanoparticles. Moreover, S-1 exhibits superior cycle and rate capacitance. The reversible capacity of S-1 can reach 1309 mA h.g(-1) after 100 cycles at 0.1 A.g(-1). Even at 2 A.g(-1), the reversible capacity of S-1 still maintains 550 mA h.g(-1). The excellent electrochemical performance of S-1 profits from its unique 3-D structure, accelerating the charge transfer rate in the conversion reaction in the lithiation/delithiation process. It believes that this work will inspire the variation of structural design in transition metal oxides (TMOs) and graphene composites as anode materials for LIBs.