This paper addresses the failed energy cooperation in experiment of muti-level Surge Protective Device (SPD).In accordance with the requirement of JB/T 10618-2006,a model of muti-level SPD is constructed and analyzed by transmission line theory and Kirchhoff law.Theoretical analysis and precise calculation show that resistance or inductance type of decoupling component works well when the protected equipment is working in status of low frequency;while only resistance type of decoupling component with low inductance should be selected when the protected equipment is working in status of high frequency.The value of decoupling component parameters could be calculated by transmission line theory and Kirchhoff law.It's helpful for designer to choose an applicable decoupling component for multi-level SPD.