The deactivation of Ni/SiO2–Al2O3 catalyst in hydrogenation of crude 1,4-butanediol was investigated. During the operation time of 2140 h, the catalyst showed slow activity decay. Characterization results, for four spent cata-lysts used at different time, indicated that the main reason of the catalyst deactivation was the deposition of car-bonaceous species that covered the active Ni and blocked mesopores of the catalyst. The TPO and SEM measurements revealed that the carbonaceous species included both oligomeric and polymeric species with high C/H ratio and showed sheet. Such carbonaceous species might be eliminated through either direct H2 reduc-tion or the combined oxidation–reduction methodologies.