Guided by Fairclough's three-dimensional conception of discourse,especially based on the context theory in Halliday's systemic-functional grammar,within the framework of Appraisal theory,the paper attempts to do the Positive discourse analysis(PDA) of a news report on the Iran nuclear issue from the New York Times from the constructive perspective,aiming to reveal America's new attitude towards Iran.Furthermore,the paper draws upon Conceptual blending theory by Fauconnier and Turner to prove the analysis in...