Abstract: Based on the new findings of the primary cracking of heavy oil and the secondary cracking of middle streams, a MCP technology (Maximizing Catalytic Propylene from heavy oil) was developed. The first industrial trial was conducted in a commercial-scale demonstration unit of MCP with capacity of 250Kt/a from an existing ARGG unit modification. The results of industrial calibration of MCP technology show that when the atmospheric residue of Jiangsu crude oil is used as the feedstock, yields of propylene and isobutylene are 17.05% and 5.51%，respectively. RON of gasoline and  cetane index of LCO are 94.6 and 30, respectively. The total liquid yield is 80.23%. Compared with ARGG, the yield of propylene and isobutylene increases 8.09% and 2.52%，respectively，while the coke reduces 2.03%. The unit of MCP has stably run for nearly 3 years with good economic and social benefits.