The invention provides a hydrotreating catalyst and a preparation method thereof. The hydrotreating catalyst takes Mo and Ni as active metal components and P as an auxiliary agent, and a carrier is any one selected from aluminium oxide and silicon oxide. With the weight of the carrier as a reference, the content of MoO<3> is in a range of 10%-25%, the content of NiO is in a range of 2%-6%, the content of the P is in a range of 0.5%-2.5%, and the balance is the carrier. The invention also provides a preparation method of the hydrotreating catalyst. The catalyst prepared by the preparation method provided by the invention has a more reasonable distribution of the active metal components and a high utilization ratio, and not only is the metal usage amount decreased, but also the selectivity of catalysts is increased.