Abstract: The ENS (Elementary Net Systems) is derived from low Petri nets Conditions/events systems. We present in this study an approach to compute the betweenness centrality index on a depending graph of an ENS. This measure can be used not only to predict the most influential event in ENS also to detect community structure (sub-network structure). So we firstly give a new strategy to represent ENS network as an event depending graph. Then we give some definitions to compute betweenness centrality indices on this depending graph. Pathway analysis of large metabolic networks meets with the problem of combinatorial explosion of pathways. To help us better understand the organization principle of complex metabolic network, we propose to present a metabolic network with ENS. This aims to deconstruct metabolic networks into sub-networks based on the global network structure by using the betweenness index. This strategy of modeling is most adequate to apply the betweenness algorithm.