Cobalt carbide has recently been reported to catalyse the FTO conversion of syngas with high selectiv- ity for the production of lower olefins (C 2 –C 4 ). Clarifying the formation process and atomic structure of cobalt carbide will help understand the catalytic mechanism of FTO. Herein, hydrogenation of carbon monoxide was investigated for cobalt carbide synthesized from CoMn catalyst, followed by X-ray diffrac- tion, transmission electron microscopy, temperature programmed reaction and in situ X-ray absorption spectroscopy. By monitoring the evolution of cobalt carbide during syngas conversion, the wavelet trans- form results give evidence for the formation of the cobalt carbide and clearly demonstrate that the active site of catalysis was cobalt carbide.