1865年《中比條約》修約案是北洋末期「到期修約」政策的試金石，北京政府依據「情勢變遷」原則及條約中之修約條款，要求到期修約，遭到比利時拒絕後，斷然宣布舊約終止，成為中國外交史上第一個片面宣布失效的舊約。比利時政府向海牙常設國際法庭提出訴訟，北京外交部力謀對策，不久雙方妥協，展開修約談判，並完成草約。北京外交部雖未能訂立中比新約，但是已經確立舊約「期滿作廢」之先例，爭取到比利時依據「平等互惠尊重主權」原則談判新約，也渡過了常設國際法庭法理爭議的難關，為南京國民政府之改訂新約，奠定了堅實的基礎。北伐完成後，南京國民政府繼續與比剎時議訂第一個友好通商條約，但引起朝野廣泛質疑與討論。
1926-1929年中比修約研究，顯現了北伐前後中國外交發展脈絡，從北洋末期「到期修約」、「到期修改期滿作廢」到南京初期「改訂新約」的演變歷程「修約」、「廢約」兩條路線逐漸合流，北洋與南京政府外交的連續性相當明顯，有助於學界擺脫過去「革命史觀」對外交史的曲解。

The treaty revision negotiations over the Sino-Belgian Treaty of 1865 were the touchstone of the Peking Government's treaty revision policy. The Peking government deemed that treaty as unequal and raised the issue according to the treaty revision clause and rebus sic stantibus principle. After the Belgian government's rejection, Peking government announced that the treaty was terminated, and Belgium claimed China's deed unlawful to the Permanent Court of International Justice at The Hague. Soon after, both parties compromised and started to negotiate a new treaty based on principles of equality and mutual respect for territorial sovereignty. A draft was reached but formal treaty not completed before the fall of the Peking government. The Nanking government took over the negotiations, and a new treaty was signed soon afterwards.
These negotiations were important for the understandings of the diplomatic strategies between Peking and Nationalist governments over revision or abrogation the so-called Unequal Treaties. That also was important for its demonstration of the continuity between Peking and Nanking diplomacy.