「四人幫」倒台以來，華國鋒拋出了「兩個凡是」的指導原則，不僅延續著毛澤東時代以來的左傾思想，也極力阻擋鄧小平復出政壇與1976年天安門事件的平反。然而自中共十屆三中全會東山再起的鄧小平卻屢屢宣揚「實事求是」，而與「兩個凡是」形成強烈的對比。尤其是〈實踐是檢驗真理的唯一標準〉一文發表後，更是掀起一場關係到中國共產黨思想路線的大爭論。隨著實事求是、解放思想的呼聲從中共高層傳出，北京西單牆也出現了民主思潮的大字報。在結合民間與地方大員的力量下，支持實踐論觀點的老幹部們得以在中共十一屆三中全會上取得優勢，形成以鄧小平為核心的領導集體。這次會議做出把全黨工作重心轉移到社會主義現代化建設上的決策，確立了改革開放的經濟方針，也為評價文化大革命與毛澤東做了準備。因此會議不但扭轉了毛澤東時代以來的左傾思想，也改變了國家的政治路線，而成為當代中國歷史的轉折點。本文擬就大量的史料為基礎，探究中共十一屆三中全會形成政治路線轉折的經過，並就其後的發展加以探討這次會議對中國歷史發展的影響。 After the downfall of “the Gang of Four”, Hua Guofeng released his “two whatevers” notion, which continued the era of Mao Zedong’s “Leftist” ideology strongly preventing Deng Xiaoping to resurge his political arena. Hua also declared the Tiananmen Incident in 1976 as a counter-revolutionary event. However, Deng Xiaoping, who reinstated his power from the convocation of the Third Plenary Session of the Tenth Central Committee of the Communist Party, repeatedly advocated his principle of “seek truth from facts”. This principle formed a striking contrast with “the two whatevers”. When Deng’s disciples published “Practice is the Sole Criterion for Testing Truth”, the article aroused a fierce ideological debate over the line of “emancipating the mind” and “seeking truth from facts” within the Chinese Communist Party (CCP). At the time the dispute of the CCP leaders took place, the Big-Character Poster (the symbolism of the democratic ideology) appeared on the Beijing Xidan Wall. By combining the support of local governmental leaders and the public, the veteran cadres, who supported the “Seek Truth from Facts”, took the leading role at the Convocation of the Third Plenum of the Eleventh Central Committee of the Communist Party. This group of cadres formed a collective leadership with Deng Xiaoping as the leading role. At this conference the Committee of CCP decided to shift the focus of the Party to socialist modernization, to set the open and reformational economic policy, and to make the preparation for the reassessment of the Cultural Revolution and of Mao Zedong. The Committee not only corrected Mao Zedong’s “Leftist” ideology, but also changed the political routes of the Nation and of the Party. This session was a great turning point in CCP history since the founding of the People's Republic. Based on a large amount of historical data, this article researched the process of the decisive ideological turn in the Third Plenum of the Eleventh Party Congress. It also discussed the impact of this conference on the development of Chinese history.