The invention belongs to the technical field of catalysts, and relates to a molybdenum-containing catalyst and a preparation method and application thereof. The catalyst comprises a catalytic active substance, wherein the catalytic active substance comprises metal molybdenum or a compound thereof; and elemental molybdenum in the metal molybdenum or the compound thereof is composed of non-radioactive isotopes with composition and/or abundance which is changed compared with natural composition and/or abundance, and the abundance of at least one non-radioactive isotope is changed by more than 1/20 and not less than 20% on the basis of natural abundance. According to the invention, the prepared molybdenum-containing catalyst has better catalytic performance.