DCC is a new technology derived from FCC for propylene production. The propylene yields can reach 23m% with paraffinic feed and around 17m% with intermediate base feed. A portion of DCC cracked naphtha recycled in a commercial unit resulted in a propylene yield increment of 3.5m% at some expense of naphtha. The total BTX in the 75 - 150℃ naphtha fraction was 57. 6v%, in which toluene and xylenes were 21.9v% and 30.3v%, respectively. DCC catalyst consists of a modified mesopore zeolite with pentasil structure for primary product of naphtha range to undergo secondary cracking for producing light olefins. A series of DCC catalysts was formulated for various objectives, such as maximum propylene, maximum isoolefins, and metal tolerance for residual oil processing, etc. Seven commercial units have been put into production since 1990 inside and outside China, in which three of them were revamped from existing FCCUs,and the other four were grassroots units including a 750kt/a unit in TPI Company, Thailand. Currently, the TPI unit is running in full design capacity with about 40m% of atmospheric residual oil in the feedstock.Although the feedstock is much heavier than design, the propylene yield still keeps around the design value.The commercial experiences of some units are presented.