Hydrocracking process and system

A hydrocracking process, comprising:

• (1) in a hydrotreating unit, a mixture of gas oil feedstock and hydrogen gas is reacted by successively contacting a hydrogenation protection agent, an optional hydrodemetallization catalyst, and a hydrorefining catalyst, to produce a reaction effluent;
• (2) in a first hydrogenation cracking unit, the reaction effluent obtained from step (1) is sent to the first hydrogenation cracking unit, and reacted by contacting a hydrogenation cracking catalyst I in presence of hydrogen gas, the resulting reaction effluent is separated to at least produce light fraction I and heavy fraction I;
• the light fraction I is rich in paraffins, the mass fraction of paraffins in the light fraction I is at least 82%, the heavy fraction I is rich in naphthenes and aromatics, in hydrocarbon composition of the >350° C. fraction of the heavy fraction I, the sum of the mass fractions of naphthenes and aromatics is higher than 82%,
• the hydrogenation cracking catalyst I comprises a support and an active metal component, the support comprises a heat-resistant inorganic oxide and a molecular sieve, the heat-resistant inorganic oxide is one or more of silica and alumina, the active metal component is at least two metal components of Group VIB metals and Group VIII metals;
• the molecular sieve is one or more of molecular sieves ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-48, ZSM-50, IM-5, MCM-22, and EU-1;
• (3) in a second hydrogenation cracking unit, the heavy fraction I obtained in step (2) is sent to the second hydrogenation cracking unit, and reacted by contacting a hydrogenation cracking catalyst II and/or a hydrotreating catalyst in presence of hydrogen gas, the resulting reaction effluent is separated to at least produce light fraction II and heavy fraction II.