The　relationship　between　the　size　of　difference　resonator　phase　diagram　and　the　amplitude　of　a　signal　to　be　detected　was　verified　through　simulation　tests.　The　larger　the　difference　resonator　phase　diagram,　the　larger　the　amplitude　of　the　signal,　under　a　condition　of　all　the　same　parameters.　The　relative　size　of　the　signal　amplitude　was　obtained　from　the　difference　resonator　phase　diagram.　According　to　characteristics　of　difference　resonator　phase　diagram,　a　new　method　was　proposed　to　identify　a　difference　resonator　phase　diagram.　At　last,　an　equipment　failure　and　its　development　process　were　found　through　anzlyzing　the　data　measured　from　a　factory.　Its　difference　resonator　phase　diagram　was　identified　and　the　desired　results　were　obtained.