外交與戰爭是國家處理國與國之間政治問題兩個主要的工具，前者是以談判來處理國與國之間的關係，而戰爭的爆發，則是象徵外交的失敗。三國鼎立之初，如何確保各領轄地之完整，如何強化內部之整頓與建設，是當務之急。於是各國之間的和平相處，是企望，也是必須的。在此考量之下，三國之間外交發展更勝於戰爭。 一般言，外交政策的發展與各政權內部發展情況有密切的關係，如曹魏政權，不論在曹操時期的挾天子以令諸侯，或曹丕以後掌握北方，擁有三國中最多的土地及資源，這些優勢使得曹魏在發展其外交策略時姿態較高，也因為實力雄厚，使其往往捨外交而直接取決於戰爭。反觀吳、蜀，在土地、人口甚至政治資本都不如曹魏的情勢下，往往必須透過結盟來制衡曹魏。但在曹魏勢力趨弱，或吳、蜀本國國勢強大的情況下，這種因現實政治利益而結合的盟約，很容易出現變化。 無論是例行性或是有特殊目的的交聘，其中最重要的就是「使節」的選派。一位優秀的使者，往往能為出使國爭取最大的利益。由於三國分合不定，使節在處理外交事務時充滿著困難與危險，所擔負的責任亦較重，是以三國所選派的使臣皆一時之選，口才、反應、文采以及對時局的瞭解為必備條件。自赤壁戰後，在魏、蜀、吳三個勢力互動中，有不少極佳的外交人才在三政權間縱橫。 本文希望透過對三國時期交聘史料的爬梳，一方面分析三國的外交背景，另一方面則展現三國時期使節所擔負的外交任務及使節選派的特色。

Diplomatic manipulation and wars were the two main tools that were used in dealing with political problems between two countries during the disunited period of the Three Kingdoms. The former was used to negotiate the conflict between kingdoms and the breakout of war was a symbol of diplomatic failure. During the earlier years of the Three Kingdoms, the priority for each kingdom was to ensure the complete control of its territories as well as to strengthen its internal construction and consolidation. Therefore, peace keeping was necessary and expected as well. Under these considerations, diplomacy was far more important than war. Generally speaking, for each kingdom there was a close relationship between the development of diplomatic policy and its internal stability. For example, Tsao Tsao and his son Tsao Pe had the control of the most fertile lands and bounteous resources among the Three Kingdoms. This advantageous position provided Tsao Wei with a higher hand in handling diplomatic policy with its rivalries. With solid backup behind them, Tsao Wei would go to war instead of seeking diplomatic solutions. On the other hand, without the abundant resources in land, population, and political power as Tsao Wei, Wu and Shu had to form an alliance to oppose Tsao Wei. However, this alliance, which was formed as a result of political gain and practicality, could change quickly whenever Tsao Wei lost its power or Wu and Shu gained strength. Whether the purpose was routine or goal-oriented diplomacy, the chosen diplomat would strive for the best interest of the country. Especailly during the period of disunity, most diplomats would face and deal with dangerous and difficult situations. Therefore, the diplomats during that period were very witty, talented, and literary gifted. Since the Battle of the Red Cliffs, the power struggle among Wei, Su, and Wu provided many skillful envoys with the opportunity to seek various allegiances among the Three Kingdoms. The purpose of this paper is, through the detailed research of the historical documents in diplomacy of the Three Kingdoms, to analyze the diplomatic background of the Three Kingdoms and to reveal the mission of the diplomats as well as the characteristics of choosing the proper envoys for the job.