The postwar negotiation after the Third War of Goryeo and Khitan (1014-1020) prevented serious wars between the two dynasties as the Chuanyuan Treaty (1004) did between Khitan and Song. The two major power of Northeastern Asia, Song and Khitan accomplished to establish stable relations through consistent exchanges of the regular celebrating envoys such as envoys on the New Year’s day and envoys on the emperor’s birthday. The unique point is that the Khitan empress dowagers were also the official receiver of the celebrations sent by the Song emperors；empress dowager Chengtian (承天太后) who had been the leader of the Khitan court at the Chuanyuan treaty is possibly the one who ignited this incomparable diplomatic practice. The empress dowagers’ active roles in the diplomatic scene between two dynasties ended with the case of empress dowager Xuanren (宣仁太后) of the Song who even dispatched envoys to the Khitan under her own title. At least two significant legacies of many of the Chuanyuan Treaty were disseminated to the Khitan-Goryeo relations. Those are the diplomatic status of the Khitan empress dowager and the consistent practice of sharing celebrations by exchanging regular envoys on the occasions mentioned above. The Khitan, during the postwar negotiation with the Goryeo in 1022, reduced the number of regular envoys down to twice per year；once on the birthday of the emperor with the New Year’s envoy, and once on the birthday of empress dowager. Interestingly there was no empress dowager alive in the Khitan court at that moment. This means that the diplomatic role of the empress dowager Chengtian was so prominent that the post of empress dowager became one of the most diplomatic representatives of the Khitan power. Since she was the one who officially acknowledged the Goryeo- Khitan border settlement in 994 the Goryeo court could urge Khitan to stop under the empress dowager’s name whenever they illegally invade the northeastern border of Goryeo.