诗题所谓的永乐公主其实是玄宗朝东平王的外孙女杨氏，嫁给了契丹王李失活，杨氏因为和亲番邦有功，依惯例被封为了公主。孙逖为唐朝官员，因此诗里用夸张的形容描绘了永乐公主的美丽，并且表现了当时卢龙塞荒凉的面貌。

《观永乐公主入蕃》 孙逖

边地莺花少，年年未觉新。
美人天上落，龙塞始应春。

Princess Yongle on the Frontier
Sun Ti

Orioles and flowers are few on frontier;
Nor new birds nor new flowers come with new year.
The fair princess seeems to fall from the Sky;
Spring comes to Dragon Fortress far and nigh.