The　FPGA　can　customize　the　array　of　internal　logic　at　will,　and　can　be　programmed　in　real　time　at　the　user＇s　site　to　modify　the　internal　hardware　logic　to　achieve　any　logic　function.　This　is　impossible　for　ASIC　and　DSP.　In　this　setting,　hardware　Trojan　is　a　malicious　circuit　intentionally　implanted　in　a　chip　or　electronic　system　or　a　defective　module　left　unintentionally　by　the　designer.　Under　special　conditions,　the　module　can　be　used　by　attackers　to　achieve　destructive　functions.　The　inserted　hardware　Trojan　may　cause　information　leakage,　change　the　circuit　function,　and　even　destroy　the　circuit.　In　this　paper,　we　use　Ring　Oscillator　(RO)　to　construct　a　ring　oscillator　network　(RON)　and　monitor　the　power　supply　of　whole　FPGA　device.　This　method　applies　the　frequency　of　the　ring　oscillator　as　a　sensitive　factor　to　facilitate　the　non-destructive　detection　of　the　location　of　the　Trojan.　©　2020　IEEE.