The invention relates to the field of petrochemical engineering, and discloses a nozzle device, a catalytic cracking system and a nozzle dredging method. The nozzle device comprises a nozzle (10) anda dredging mechanism (11); the dredging mechanism comprises a dredging pipe (110) communicating with the nozzle and capable of introducing a medium with pressure into the nozzle to dredge the blockednozzle, and a sealing piece sleeving the dredging pipe for sealing the dredging pipe; and the sealing piece is provided with a guide leaching port (126) for discharging the medium with pressure afterthe blockage is dredged. The nozzle device not only can dredge the blocked nozzle online to effectively dash away blockage matters, but also can effectively prevent the influence on the product quality and yield. The device is applied to the catalytic cracking system, and effectively dredges the blockage matters in the raw material nozzle. The nozzle dredging method effectively dredges the nozzle,prevents the influence on the product quality and yield, and is convenient to operate and high in repeatability.