The social network analysis theory was used to explore two domestic petrochemical companies on their environmental, safety, and health (ESH) management system and operation effectiveness. Both qualitative and quantitative analyses by NodeXL and statistical tools were applied through the survey questionnaires to observe the results of social network among two management systems. From the background information of those individuals, parameters and network diagrams, we could identify three kinds of specialized network personnel: Central persons, marginal men and information agents, in order to understand the organization work, and information flows and influence patterns. Two companies showed differences in their International Standard Organization (ISO) based management systems and actual functioning systems. The centrality parameter indicated that some managers lack network connections to others and some members' knowledge could not be adequately used owing to the faults in organization structures. These problems would lower the effectiveness of management systems. Our analysis also showed positive correlations between the trustworthiness among members as well as the recognition networks. This study showed that the network analysis could be a good reference for the high-level managers to understand their ESH system, to evaluate the organization efficiency and to analyze their future development and operation needs. (C) 2017 American Institute of Chemical Engineers