The invention discloses a combined treatment method for coal tar-residual oil hydrocracking, catalytic cracking and diesel aromatics extraction. The method includes: subjecting coal tar to pressure reduced distillation to obtain light coal tar and heavy coal tar; mixing the light coal tar with residual oil, and then carrying out hydrocracking reaction to obtain gas, gasoline, diesel, pressure reduced gas oil and tail oil; mixing the tail oil with the heavy coal tar, and carrying out catalytic cracking reaction under supercritical conditions, thus obtaining cracked gas, catalytically cracked gasoline, catalytically cracked diesel, heavy distillate oil and cracked oil slurry; mixing the diesel obtained by hydrocracking with the catalytically cracked diesel, then performing aromatics extraction, partly or totally returning the extract oil and catalytically cracked heavy distillate oil to a catalytic cracking device to undergo cracking reaction, and discharging the raffinate oil out of the device so as to obtain high cetane number diesel. The method provided by the invention can improve the conversion rate of the raw materials, reduce coking, increase the yield of light oil and prolong the service life of the catalytic cracking catalyst, thus obtaining a high cetane number diesel component.