The sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) restricts the practical application of Li-O2 batteries. The design and facile synthesis of cathode catalysts with high activity on both ORR and OER are desired. In this study, an ultrathin N-doped defective carbon layer-encapsulated W2C hybrid (W2C@NC) which has been successfully synthesized through a facile in-situ pyrolysis and reduction of WO3@g-C3N4 shows a high activity on ORR, OER and even the decomposition of the undesired Li2CO3 as a multifunctional cathode catalyst for Li-O2 batteries. The cells catalyzed by W2C@NC show a much higher initial capacity of 10976mAhg−1, lower overpotential and longer cycle life, which can be largely attributed to the synergistic effect of W2C nanoparticles and the ultrathin defective N-doped carbon layers. The unique architecture not only accelerates the electron and Li+ conduction but also provides more active sites, which lead to the large enhancement of the electrocatalytic performance. In addition to the high activity on both ORR and OER, W2C@NC also shows a high catalytic function on the decomposition of the undesired side product of Li2CO3. This study offers some new insights into the design and synthesis of novel high performance cathode catalyst for Li-O2 battery.