Derivation of 10‑oxo‑6,1‑dihydrobenzo [e] pyrido [1,2‑c] [1,3] oxazine‑9‑carboxylic acid of formula (I) as an inhibitor of hepatitis B surface antigen Substance, or a pharmaceutically acceptable salt thereof, and the use of a compound of formula (I) or a pharmaceutically acceptable salt thereof and a pharmaceutical composition thereof in the preparation of a medicament for treating hepatitis B virus.作爲乙肝表面抗原抑制劑的式(I)的10‑氧代‑6,1‑二氫苯并[e]吡啶并[1,2‑c][1,3]惡嗪‑9‑羧酸衍生物,或其藥學上可接受的鹽,以及式(I)化合物或其藥學上可接受的鹽和其藥用組合物在製備治療乙型病毒性肝炎的藥物中的應用。