1937年,日人(ren)鳥山喜一、藤田亮策等對八連城(cheng)進行了(le)調查(cha),并對八連城(cheng)內城(cheng)宮(gong)殿址進行了(le)盜掘(jue)。
中(zhong)華人(ren)民(min)共和(he)國成立(li)以后,吉林省各級文(wen)物管理部門對城址開展了多次調查和(he)著錄(lu)工作。
2004至2008年,吉(ji)林省(sheng)文(wen)物考(kao)古研究所、吉(ji)林大(da)學、琿春市文(wen)物管理所等單位,對城(cheng)址(zhi)進行了(le)主動發掘。主要清理了(le)一、二號宮殿基址(zhi)及(ji)其附(fu)屬建(jian)筑遺跡,城(cheng)門址(zhi)等。出土(tu)大(da)量磚、瓦類建(jian)筑構件。
經考古發掘確認的城(cheng)(cheng)(cheng)門(men)(men)有兩(liang)處(chu),分別為(wei)外城(cheng)(cheng)(cheng)南門(men)(men)址和內城(cheng)(cheng)(cheng)南門(men)(men)址。外城(cheng)(cheng)(cheng)南門(men)(men)址規模(mo)較小,單門(men)(men)道(dao),東(dong)西(xi)寬(kuan)約3.2、南北(bei)長(chang)約5.2米(mi)(mi)(mi),直接利(li)用城(cheng)(cheng)(cheng)墻(qiang)墻(qiang)體作為(wei)城(cheng)(cheng)(cheng)門(men)(men)兩(liang)側的墩臺(tai)(tai)。內城(cheng)(cheng)(cheng)南門(men)(men)為(wei)建有夯土臺(tai)(tai)基的地(di)面(mian)建筑。臺(tai)(tai)基呈長(chang)方形,南北(bei)寬(kuan)16.2米(mi)(mi)(mi),東(dong)西(xi)長(chang)27.4~28.6米(mi)(mi)(mi),東(dong)西(xi)兩(liang)端正中與城(cheng)(cheng)(cheng)墻(qiang)相(xiang)接,現(xian)高0.6~0.8米(mi)(mi)(mi)。臺(tai)(tai)基上可(ke)見面(mian)闊五間,進深二間的圓形柱礎基礎。臺(tai)(tai)基南、北(bei)兩(liang)側各有三條兩(liang)兩(liang)相(xiang)對,以黃色(se)夯土構筑的踏道(dao)。
內城的縱向中軸線上,有(you)2座宮(gong)殿(dian)(dian)址(zhi),分別為一(yi)(yi)、二號(hao)宮(gong)殿(dian)(dian)址(zhi),兩(liang)座宮(gong)殿(dian)(dian)址(zhi)兩(liang)側(ce)均有(you)附屬(shu)建筑,東西兩(liang)端各與一(yi)(yi)條南北(bei)向長廊(lang)相接,兩(liang)殿(dian)(dian)址(zhi)間有(you)一(yi)(yi)“十”字形建筑臺基建筑。
城(cheng)內出(chu)土(tu)遺物(wu)以建筑構件(jian)為(wei)(wei)(wei)(wei)主,包(bao)括板(ban)瓦(wa)(wa)、筒瓦(wa)(wa)、瓦(wa)(wa)當(dang)、獸頭、套(tao)獸、鴟尾、柱圍等。瓦(wa)(wa)件(jian)多(duo)為(wei)(wei)(wei)(wei)青灰色,但仍不乏(fa)為(wei)(wei)(wei)(wei)數不少的黃、綠(lv)釉琉璃瓦(wa)(wa)件(jian),瓦(wa)(wa)當(dang)當(dang)面紋飾以六瓣和八瓣蓮花(hua)(hua)紋為(wei)(wei)(wei)(wei)主,另見(jian)有(you)花(hua)(hua)草文、乳(ru)丁紋等。出(chu)土(tu)的瓦(wa)(wa)件(jian)中有(you)相當(dang)一(yi)部分(fen)瓦(wa)(wa)身(shen)凸面帶有(you)文字,或戳印(yin)、或刻(ke)畫(hua),陰文、陽文均有(you),多(duo)數為(wei)(wei)(wei)(wei)漢字,少量為(wei)(wei)(wei)(wei)刻(ke)畫(hua)符號(hao),累計出(chu)土(tu)九十(shi)余(yu)種。
該城的布局(ju)與(yu)渤海(hai)上京(jing)(jing)、中京(jing)(jing)相仿,均效仿于唐(tang)長安城,具有(you)重(zhong)要的歷史價值。
從城(cheng)址(zhi)規模、布(bu)局、主體建筑形式設計等方面比較,八(ba)連城(cheng)城(cheng)址(zhi)與渤海(hai)中京顯德(de)府城(cheng)址(zhi)(和龍西(xi)古城(cheng))極(ji)為(wei)相似(si)。這(zhe)兩座城(cheng)址(zhi)的發掘,為(wei)渤海(hai)及東北(bei)亞都城(cheng)研究(jiu)提供了(le)重要(yao)的考古學資(zi)料。
渤海(hai)國(guo)(guo)(guo)城(cheng)(cheng)(cheng)(cheng)址(zhi)。位于(yu)(yu)琿春(chun)(chun)市國(guo)(guo)(guo)營(ying)良(liang)種(zhong)場內(nei)(nei),東(dong)距(ju)琿春(chun)(chun)市6公(gong)里,北(bei)(bei)l公(gong)里是(shi)圖(tu)(們(men))琿(春(chun)(chun))公(gong)路。城(cheng)(cheng)(cheng)(cheng)址(zhi)由內(nei)(nei)外(wai)兩(liang)城(cheng)(cheng)(cheng)(cheng)組成。外(wai)城(cheng)(cheng)(cheng)(cheng)平(ping)面略呈方形,城(cheng)(cheng)(cheng)(cheng)墻(qiang)(qiang)(qiang)(qiang)土(tu)筑(zhu)。周(zhou)(zhou)長(chang)2894米(mi),北(bei)(bei)墻(qiang)(qiang)(qiang)(qiang)712米(mi),南(nan)墻(qiang)(qiang)(qiang)(qiang)701米(mi),東(dong)墻(qiang)(qiang)(qiang)(qiang)746米(mi),西墻(qiang)(qiang)(qiang)(qiang)735米(mi)。城(cheng)(cheng)(cheng)(cheng)有4門(men),分(fen)別設置于(yu)(yu)各(ge)墻(qiang)(qiang)(qiang)(qiang)的中部(bu),城(cheng)(cheng)(cheng)(cheng)墻(qiang)(qiang)(qiang)(qiang)外(wai)6米(mi)處(chu)有護城(cheng)(cheng)(cheng)(cheng)河遺跡。內(nei)(nei)城(cheng)(cheng)(cheng)(cheng)平(ping)面呈長(chang)方形,周(zhou)(zhou)長(chang)l072米(mi),南(nan)、北(bei)(bei)墻(qiang)(qiang)(qiang)(qiang)各(ge)長(chang)218米(mi),東(dong)、西墻(qiang)(qiang)(qiang)(qiang)各(ge)長(chang)3l8米(mi),有城(cheng)(cheng)(cheng)(cheng)門(men)3處(chu),分(fen)別修建于(yu)(yu)南(nan)、東(dong)、西墻(qiang)(qiang)(qiang)(qiang)的中部(bu)。內(nei)(nei)城(cheng)(cheng)(cheng)(cheng)中央有一宮殿址(zhi)臺(tai)基,臺(tai)基北(bei)(bei)另有殿址(zhi)3處(chu)。出土(tu)文物有蓮花(hua)紋(wen)瓦當、“文字(zi)”瓦、浮雕式牡丹紋(wen)和忍冬紋(wen)磚(zhuan)、綠釉(you)琉璃瓦等(deng)。八(ba)(ba)連城(cheng)(cheng)(cheng)(cheng)是(shi)唐(tang)(tang)代渤海(hai)國(guo)(guo)(guo)東(dong)京(jing)龍(long)原(yuan)府(fu)遺址(zhi),始建于(yu)(yu)唐(tang)(tang)德宗貞元元年(nian)(nian)(785)左右。唐(tang)(tang)貞元時,渤海(hai)第三代王大(da)欽茂將(jiang)其國(guo)(guo)(guo)都從上京(jing)龍(long)泉府(fu)遷至八(ba)(ba)連城(cheng)(cheng)(cheng)(cheng),唐(tang)(tang)貞元10年(nian)(nian)(794年(nian)(nian)),渤海(hai)成王復遷上京(jing)后,八(ba)(ba)連城(cheng)(cheng)(cheng)(cheng),仍為(wei)渤海(hai)之(zhi)東(dong)京(jing)。公(gong)元926年(nian)(nian),遼滅渤海(hai),八(ba)(ba)連城(cheng)(cheng)(cheng)(cheng)遂(sui)廢(fei)。古城(cheng)(cheng)(cheng)(cheng)內(nei)(nei)現已辟為(wei)農田。
1961年吉林(lin)省人(ren)民委員會公布為(wei)吉林(lin)省重(zhong)點文物(wu)保(bao)護單位。
2001年6月(yue)25日國務院(yuan)公布為全國重點(dian)文物保護單位。