Abstract: As the feedstocks of delayed coker become heavier and inferior, there are more challenges for coker unit，such as higher liquid product yield , long-term and safe operation, environmental protection and capacity of the unit. A new process named ADCP which integrates a mild thermal cracking stage with a deep thermal cracking stage with one furnace in a coking unit is realized by LPEC for higher liquid product yield. Studies were conducted in LPEC pilot plant with visbreaking, delayed coking and continuous distillation to investigate the effect of heavy oil mild thermal cracking depth on the properties and compositions of coking products. The results show that the yields of liquid products are improved by 0.48, 0.97 and 1.71 percent, respectively when visbreaking ratios of heavy oil are 33.03, 52.43 and 78.21 percent. The yields of light liquid products are increased by 1.04, 1.11 and 2.19 percent, respectively, compared with that of the traditional process. The improvement in light oil yields is mainly manifested in yield increase of the diesel fraction. However, the properties of ADCP products are almost the same as the ones of traditional process products, so the new process has no negative effects on down-stream processes.