The invention provides an oil-soluble self-vulcanizing molybdenum catalyst, and a preparation method, a use method and an application of the oil-soluble self-vulcanizing molybdenum catalyst. The preparation method comprises the following steps of (1) sequentially putting a molybdenum source, water, sodium sulfide, a solvent and inorganic acid in a container under the protection of nitrogen, uniformly mixing and stirring, cooling to 5-50 DEG C for reaction for 10-150min, (2) adding alkylamine and carbon disulfide, uniformly stirring, heating to 60-200 DEG C for reaction for 3-10h, and (3) after reaction, sufficiently cooling a product, performing suction filtration, sufficiently washing with methanol, and drying to obtain the oil-soluble self-vulcanizing molybdenum catalyst. The oil-soluble self-vulcanizing molybdenum catalyst can be vulcanized and decomposed to form a molybdenum disulfide active component in situ, is used for a slurry reactor hydrocracking technology for poor heavy oil with a high metal content, a high carbon residue content and a high sulfur content, can reduce the coke yield, and keeps long-period operation of a device.