Nonaqueous Li-O2 batteries are of great interest because of their high theoretical energy density, and a stable porous cathode plays a vital role in electrochemical performance of Li-O2 batteries. Herein, catalyst nanoarchitecturing via functionally implanted cobalt nanoparticles in N-doped carbon host is fabricated by an ultrasonic method combined with controlled calcination process and served as an effective electrocatalyst for Li-O2 batteries. The synthesized catalyst holds a three-dimensional porous network structure, which could offer numerous active sites and provide the channels for mass transfer. When employed as an oxygen electrode, the Li-O2 battery shows improved discharge capacity of 3862 mA h g−1 at a current density of 0.1 mA cm−2 and superior cycling stability up to 40 cycles with a limited capacity of 500 mA h g−1, owing to the porous carbon substrate with highly graphitic and better catalytic activity of implanted Co nanoparticles. The N-doped carbon with a high degree of graphitization is obtained by a catalytic pyrolysis method and Co as main catalyst also give a good reference for future design of efficient catalysts for electrochemical application.