Decision making support has become essential to conduct an effective management and operational system. It is considered an important part of operational research and management science. There are various decision issues concerning the good governance and management of a supply chain. In this paper, we focus on the conception problem of a supply chain, especially the geographical location implementation of the facilities, also known as multi-facility Weber problem. In fact, business location is considered a strategic decision; it was the focus of various studies in the literature. We propose in this paper an improved approach to solve the multi-facility location decision. The methodology is based on mathamatical modeling using the partition theory and Voronoi diagram in order to define the facilities locations and their assigned demand points (customers). Our objective is to design a network respecting the environmental and economical factors. The obtained results are represented as a diagram defining the subdivisions, the partitions of demand points and the locations of the facilities.