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The problem of pick sequencing in the rotary rack S/R system (PPS-RRS) is investigated with the objective of minimizing the execution time.The rotary rack S/R system consists of one S/R machine and multiple levels of carousels that can rotate independently in bi-directions.The routing policy,namely the decision on the storage or retrieval sequence,dominates the efficiency and the throughput for such S/R systems,due to the complicated relationship between all levels of carousels and the S/R machine.For the purpose of optimizing the PPS-RRS,a computational model is developed in terms of execution time for picking multiple items in one trip.Characteristics of the PPS-RRS are analyzed and a local search heuristic based on a newly proposed neighborhood is presented.Integrated with the proposed local search procedure a new hybrid genetic algorithm is developed.Experimental results demonstrate the structure characteristics of good sequence and the efficiency and effectiveness of the proposed sequencing algorithms.