The invention relates to the technical field of petroleum refining, in particular to a hydrocracking and catalytic cracking combined process and device. The hydrocracking and catalytic cracking combined process comprises the following steps: a) carrying out hydrocracking treatment on residual oil raw materials, then collecting heavy oil for catalytic cracking treatment, and collecting diesel oil fractions or gasoline fractions; and b) carrying out catalytic cracking treatment on the diesel oil fractions or gasoline fractions again, and collecting the products, wherein hydrofining pretreatmentis carried out on the diesel oil fractions before the catalytic cracking treatment is carried out again, and the initial distillation point of the heavy oil is 160-350 DEG C. The device comprises a hydrocracking reactor, a catalytic cracking reactor and a fractionation unit, wherein the hydrocracking reactor is connected with the catalytic cracking reactor, and the catalytic cracking reactor is connected with the fractionation unit. According to the invention, the hydrocracking and catalytic cracking combined process can be optimized according to market change, a large amount of liquefied gasor gasoline with a high added value can be flexibly produced, and the economic benefit is improved.