西漢都長安，以關中為帝國之中樞及根本之地，又徙天下豪強、吏二千石以實三輔，經營關中二百餘年。然光武中興，不沿西漢之舊，以關中長安為都，而別建新都於河南之洛陽。本文考論光武以洛陽為首都之原因如下：其一、光武不都長安而都洛陽，蓋關中生產之糧食不能支持帝國之首都，必須每年自東方轉漕數百萬石糧食入關，耗費極大。其二、漢代經學的特色之一是以讖諱說經。西漢後期，讖緯已有洛陽位於天下之中，天子當徙都其地之說。王莽之時，符命且明謂洛陽為帝都。光武信奉圖讖，讖書言洛陽乃帝都之地。此說必影響光武定都洛陽之決定。其三、高祖立基於蜀漢關中，出與項羽爭天下，自易接受建都於關中。光武與群雄爭天下時，以河北、三河為後方，則光武以洛陽為首都，亦自然而理順。至建武12年11月乃夷滅巴蜀公孫述，統一天下，其時上距以洛陽為都已十餘年，因繼續都洛陽。其四、光武性格平實低調，少遠大空泛之志，但求安穩無事。其選洛陽為都，蓋居於內部中心之地，較為安全。不欲如西漢之都關中，與羌、氐相鄰，暴露在外，易見侵擾。且光武既無西向拓地之心，亦無必要都關中。東漢以洛陽為帝國之首都，本文論其影響如下：其一、關中地區之衰落。西漢關中為全國政治重心地區，亦為經濟文化發達地區之一。光武定都洛陽，政治中心東移，三輔戶口大減，羌戎入侵。東漢後期，三輔之居民，「華夷居半」，三輔實成邊郡。其二、東漢都洛陽，不但不復經營關中，且放棄西邊、西北邊部份郡縣。東漢西北邊界乃在戎狄不斷向東向南推進之下，漸向東南移。安帝、順帝時期，漢廷築千餘塢壁，形成一新防禦線，并州、涼州位於線外，以防禦南匈奴與諸種羌等入居塞內之邊疆民族對內郡之侵擾。朝廷又有棄涼州之議，「徙民逃寇」之實。其三、光武都洛陽，遠離邊塞，朝廷不欲耗費，經營萬里之外無用之地。建武21年，西域諸國「皆遣使求內屬，願請都護。」光武不許。此確定東漢政府對西域政策之主調：放棄西域。

The imperial capital of Western Han Empire ChangAn（長安）was located in the territory GuanZhong（關中）where was the most important part of the Empire and was near the area of the nomadic tribes. When emperor GuangWu （光武皇帝）overcame his rivals and built the Eastern Han Empire, he put his capital on the city of LoYang which is situated in the middle of the Empire. The reasons for that emperor GuangWu chose the city of LoYang as capital of Eastern Han Empire are below: 1. The agricultural productions in the territory GuanZhong was not sufficient to support imperial capital; the government had to transport millions hundredweight of foods from the East every year in the time of Western Han Dynasty. 2. The superstitious talks in the time that LoYang located in the middle of the world, it should be the capital of the son of haven. This thought could determine the decision of emperor GuangWu for the issue of choosing imperial capital. 3. When emperor GuangWu was fighting his rivals for building Eastern Han Empire, he occupied firstly the territory in the north of Yellow River and the territory around LoYang. These places were his back-up base in the war time, and he took LoYang as his capital naturally. 4. Emperor GuangWu was practical man who had not much hollow ambitions. He chose LoYang as imperial capital for the safety, for LoYang was far from the western nomadic tribes. The influences of LoYang as the capital of Eastern Han Empire we discuss in this article are below: 1. The decline of the territory GuanZhong in Eastern Han Dynasty. This territory was the most important political economical and cultural center of Western Han Empire. In Eastern Han Dynasty, the imperial capital was not in the territory GuanZhong, this territory lost political importance, the population of this territory diminished fast, and half population was nomads. 2. Imperial capital LoYang was situated in the middle of the Empire, the Eastern Han government, encountering the nomadic tribes, withdraws from the frontier and abandoned a large part of the western and northwestern territory of the Empire. 3. Eastern Han government abandoned also the territory of central Asia where was controlled by the officers sent by the Western Han government since the reign of emperor Wu.