His father was Kim Hyo-yang, and his mother was Lady Gye-o, the daughter of Park Chang-do.

Wonseong's queen was Lady Yeonhwa, the daughter of Gakgan Kim Sin-sul.

From this point of view, he is a figure closely related to his appearance and has been opposed to the monarchy of the royal family since King Gyeongdeok.

After Seondeok died without an heir, the nobles chose Wonseong as the new king.

In 788, he established the national civil service examination for the first time, on the Tang model.