Nanosized WC/C catalyst was synthesized via a novel ultra-rapid confinement combustion synthesis method. Result showed that the amount of activated carbon (AC) played an important role in the morphology and structure controlling of both the precursor and the final powder. Due to the confinement of the pore structure and large specific surface area of AC, the WC particles synthesized inside the pores of AC had the size of 10-20 nm. When applied to oxygen reduction performance, the half-wave potential was -0.24 V and the electron transfer number was 3.45, which meant that the main reaction process is the transfer of four electrons. The detailed electrocatalytic performance and the underlying mechanism were investigated in this work. Our study provides a novel approach for the design of new composition and structure catalysts which has a certain significance for promoting the commercialization of fuel cells.