The invention discloses a hydrocracking commencement method which comprises the following steps: firstly, introducing low-
nitrogen commencement oil,
hydrogen and a vulcanizing agent into a hydrocracking device, carrying out constant-temperature
vulcanization on a hydrocracking catalyst at 220-260 DEG C, when the content of
hydrogen sulfide in circulated
hydrogen is up to 3000-5000ppm, reducing theaddition velocity of the vulcanizing agent, and increasing the temperature of a hydrocracking catalyst
bed layer, when the temperature of the hydrocracking catalyst
bed layer is up to 310-330 DEG C,increasing the addition velocity of the vulcanizing agent, continuously carrying out constant-temperature
vulcanization, increasing the temperature to 380-390 DEG C, and introducing
raw material oil to carry out a reaction, wherein the hydrocracking catalyst has 0.3-4% by weight of a
nitrogen element, and the
nitrogen element is derived from low-molecule-weight
nitride and strong alkali cyclic
nitride. The method is short in time for commencement,
raw material switching and stable production state start, the consumption of a passivant in the commencement process and potential danger in the
ammonia injection process can be avoided, and not only is
energy consumption reduced, but also environment
pollution and
human body damage caused by the passivant can be reduced.