关键词: 多项目, 双目标, time-cost置换

Abstract: For the time-cost trade-off problem with multi-project condition，this paper develops a bi-objective model that the decision variables are the allocated resource quantities，and the objective functions are the projects delay（to be minimized）and the project costs（min）.After summarizing other researchers’ multi-objective evolution algorithms and considering the characteristics of multi-project，this paper puts forward a local direct search technology based on Nondominated Sorting Genetic Algorithm II（NSGA-II）.It adopts discrete-continuous decision variables to settle the problem.Compared with NSGA-II，the approved algorithm can find the optimal solutions rapidly，moreover，for discrete variables，the algorithm can also run better.Finally，it compares the improved algorithm to ZDT test problems，the algorithm is superior similarly.

Key words: multi-project, bi-objective, time-cost trade-off