Twig　pattern　minimization　is　an　important　aspect　of　XML　query　optimization.　During　the　minimizing　process,　it　usually　needs　to　take　advantage　of　the　constraints　of　XML　Schema.　The　traditional　methods　for　identifying　constraints　is　to　develop　corresponding　algorithms　based　on　the　type　of　constraints.　It　is　inflexible　because　the　constraints　may　be　changed　as　new　Twig　pattern　optimizing　rules　are　found.　Since　the　constraints　of　XML　Schema　mainly　depict　the　sequence　relationship　of　nodes,　it　is　natural　to　be　described　by　temporal　logic.　Based　on　the　recognition,　this　paper　proposes　a　method　of　identifying　XML　Schema　constraints　using　temporal　logic.　Concretely,　an　XML　Schema　is　modeled　as　a　graph.　In　order　to　easily　represent　constraints　related　to　parent　and　ancestor　nodes,　we　made　some　modifications　to　Computational　Tree　Logic(CTL)　with　backward　temporal　operators,　and　developed　model　checking　algorithms　for　automatically　identifying　XML　Schema　constraints.　Compared　with　traditional　methods,　our　method　is　more　flexibility.