Abstract: In order to reduce the tool storage cost in a numerical control shop, it is an urgent problem to schedule and plan the required tool types based on their constituent modular types. This paper considers the problem of determining the number of modular copies of each modular type with the aim of minimizing makespan of a task with the constraint of a given budget for tool purchase. An iterative algorithm is proposed to calculate the makespan, and a heuristic algorithm is used to select the bottleneck resources. Computational experiments results show that a better tool requirements plan can be obtained in modular-based method than in tool-based one.