Lithium-rich layered oxide materials are considered as one of the most promising cathodes for high-energy lithium-ion batteries. However, their practical applications are currently restricted by its low initial Coulombic efficiency and poor rate capability and cycling stability. In this study, we report the preparation of Li1.2Mn0.54Ni0.13Co0.13O2 nanowires that have porous structures with different contents of spinel phase via a co-precipitation method followed by carefully controlled calcination steps. Structural characterizations verify that the as-prepared nanowires are composed of interconnected nano-sized subunits with porous structures, and spinel phases are embedded inside the layered structure. The electrochemical measurements show that the Li1.2Mn0.54Ni0.13Co0.13O2 nanowires bearing moderate content of spinel phase exhibit a high capacity of 291 mAh g−1 at 0.1 C and excellent capacity retention of 91.8% after 200 cycles at 1 C. The results also demonstrate that electrochemical performance of the Li1.2Mn0.54Ni0.13Co0.13O2 nanowires is influenced by the content of spinel phase which can be readily tuned by changing the heating rate in the calcination step. The combination of one-dimension porous structures and built-in spinel domains in Li1.2Mn0.54Ni0.13Co0.13O2 nanowires improves the electrolyte contact and Li+ diffusion, and restrains structural degeneration.