入聲韻之陰聲韻化爲漢語北方音韻母系統變化中最爲突出之音變。『蒙古字韻』和『飜譯老乞大·朴通事』各成書於十三世紀末和十六世紀初，各反映元代和明代之北方音，而對於硏究近代北方音的音韻系統來說，其學術價値非常高。『蒙古字韻』和『飜譯老乞大·朴通事』都反映中古入聲韻向陰聲韻之過渡階段。本文通過對元代的『蒙古字韻』與朝鮮的『飜譯老乞大·朴通事』進行對應分析，幷參照『廣韻』之音韻體系，發現中古入聲韻有如下音變;
第一，中古入聲字的韻尾一律變爲喉塞尾。
第二，[-k]韻尾有複元音化的變化。
第三，『飜譯老乞大·朴通事』不少有與『蒙古字韻』相類似的音韻系統。
第四，[-k]韻尾的一部分字在『飜譯老乞大·朴通事』里有一字兩讀現象。
第五，受聲母的影響一部分[iuʔ]韻母字發生洪音化。
Middle Chinese had entering tone with [p], [t], [k] in the coda. These three different final stops merged into the glottal stop [ʔ] in Modern Northern Chinese, and finally, they are lost stop coda and merged into yinshengyun(陰聲韻, open syllable). Mengguziyun(MGZY) is an official rhyme book compiled by the Yuan court to provide an orthography for dushuyin of Northen Dialect in Yuan dynasty. FanyiLaoqida·Piaotongshi(FYLP) are a textbook for teaching Chinese to Koreans in the early sixteenth century, and they provide evidence for the transition period from rushengyun(入聲韻, closed syllable) towards yinshengyun. This study focuses on the rushengyun and compares the phonological system between MGZY and FYLP in order to investigate changes of system in Modern Chinese.
