A dual energy imaging inspection method is proposed， which uses dual layer flat panel detector （FPD） to acquire X-ray dual energy images under single exposure， and dual energy subtraction is performed. Single layer， dual layer FPD structures are introduced， and the principle of dual layer FPD imaging is detailed as well. Different and same tube voltage with different filters induced X-ray spectra are simulated， and dual energy image characteristics of chest phantom are analyzed by performing kVp switching， dual layer FPD imaging tests. The results show that dual energy images captured by kVp switching， dual layer FPD can represent attenuation difference of soft tissue， bone with respect to low， hight energy X-rays. Dual layer FPD method owns advantages of lower exposure dose and no motion artifacts compared to kVp switching. Finally， dual energy image registration method for dual energy FPD is proposed， and bone enhanced and bone suppressed images are acquired by performing dual energy subtraction after registration. Experiment results show dual energy subtraction images using dual layer flat panel detector can realize better visualization for doctors’ diagnosis， and the subtracted images present better contrast than kVp switching method does.