A scientific and reasonable siting decision is the key to ensure the smooth operation and positive results of the project. In this paper, a grey multi-criteria decision-making (MCDM) method is proposed and applied to the siting of electrochemical energy storage station (EESS) projects. First, this paper constructs an criteria system consisting of 5 criteria and 22 sub-criteria. Second, considering the uncertainty and hesitation of decision makers (DMs), grey numbers are used to describe the evaluation information of DMs, and further decision information is mined through secondary evaluation based on the initial evaluation. Third, considering the unique situation of the EESS with many criteria, equal importance and interdependence among criteria, the improved best-worst method (IBWM) expands the scope of application to make the decision-making process more realistic. Fourth, in order to reduce the loss of information, the grey entropy method and the probability-based WISP method are proposed. Finally, the validity and feasibility of the method is verified through case studies. The results show that P2 is the optimal choice. This work has important theoretical significance and practical application value, and provides a reference basis for early decision-making of the EESS project.