The scheduling process of cracking furnace feedstock is important in an ethylene plant. In this paper it is described as a constraint optimization problem. The constraints consist of the cycle of operation

maximum tube metal temperature

process time of each feedstock

and flow rate. A modified group search optimizer is proposed to dealwith the optimization problem. Double fitness values are defined for every group. First

the factor of penalty function should be changed adaptively by the ratio of feasible and general solutions. Second

the "excellent" infeasible solution should be retained to guide the search. Some benchmark functions are used to evaluate the newalgorithm. Finally

the proposed algorithmis used to optimize the scheduling process of cracking furnace feedstock. And the optimizing result is obtained.