The study is an attempt to provide an answer to the question of whether the South Korean political leaders have a significant influence on North Korea policy during a security challenge. Specifically, does South Korea with a more cooperative leader more likely to response to the security challenges by a more cooperative policy, or do structural and domestic political constraints limit their significance? To answer the question, this thesis examines the effect of South Korea’s presidential operational code beliefs on North Korea policy in security challenges. The study assessed every president’s operational code beliefs from Kim Dae-Jung to Park Geun-hye (from 1998 to 2016), mainly focusing on the “image of the political universe” (P-1)and “strategic preference” (I-1). Operational codes were derived from the content analysis of public speeches of presidents using the computer-based Verbs In Context System (VICS). Operational code analysis findings showed that all of the president’s operational codes were significantly related to the foreign policy outcomes