2008年的俄喬戰爭是俄羅斯自解體以來第一次境外用兵，本文試圖透過守勢現實主義 ( defensive realism ) 的角度來解釋這一場俄羅斯的對外衝突。守勢現實主義國家的行為模式包括維持守勢現狀、對外尋求合作，因此得以處理安全困境難題，而在威脅等級過高時可能採取預防性戰爭來消除威脅。本文藉由守勢現實主義的觀點與行為模式來解釋俄羅斯的外交行為，透過檢視俄羅斯自解體以來的國家行為模式確立俄羅斯為守勢現實主義國家。再者藉由探討俄喬衝突中分離主義問題與俄喬關係中的矛盾以說明衝突的遠因與近因。最後探討俄羅斯在外高加索地區的利益與衝突以解釋俄羅斯在俄喬戰爭中的出兵動機。俄羅斯在解體之後的外交政策大多採取不衝突與合作的策略，隨著喬治亞的政權更替，俄羅斯對喬治亞的關係從合作走向以政策制衡，最後基於俄羅斯南部的地緣安全與北約東擴等等來自西方的威脅之下，俄羅斯採取了協助喬治亞分離地區的軍事行動來解決自身威脅。本論文認為俄羅斯不僅在2008年前屬於守勢現實主義國家，以守勢現實主義的觀點來看，俄喬戰爭更是一場為了應對歐美威脅的防禦性戰爭。 / The 2008 Russo – Georgian war was the first military action outside borders since the collapse of USSR. In this thesis, I describe the conflict using the perspective of Defensive Realism. The behavior of a state using a defensive realism perspective includes remain status-quo of defensive, seeking cooperation, therefore are able to manage the security dilemma. When the threat level is too high, a state using a defensive realism perspective may launch a preventive war to eliminate the threat. First, by examining Russia’s state behavior between 1992 to 2008. We are able to determine that Russia follows defensive realism behavior. Secondly, by studying the separatism of South Ossetia and Abkhazia in Georgia and the change of relationship between Russia and Georgia, we are able to elucidate the factors that caused the Russo-Georgian war. Finally, we explore Russia’s interests and threats in South Caucasus area that reveal the motivation for Russia the launch the counter strike against Georgia. Russia has tended to take the non-conflict route and cooperative strategy in diplomacy after Soviet-era ended. Due to the regime change in Georgia, Russia changed its policy toward Georgia from cooperative to containment. Finally, as the threat from the West rose and another round of NATO enlargement occurred, while it’s threating the geopolitical security of the southern border, Russia decided to launch a preventive war to assist the separatist states within Georgia. In conclusion, not only Russia is a defensive realism state, from the perspective of defensive realism, the 2008 Russo-Georgia war is a preventive war against the threat of the West.