Choi, who is replacing Choo Kyung-ho, will need to maintain economic momentum ahead of parliamentary elections next April, which will determine the legislative support level for a number of bills proposed by the government including the ministry's proposal to restrict fiscal spending growth.

"With this (decision) Yoon is trying to make sure there is policy continuity in place ahead of election," said Park Sang-hyun, an economist at HI Investment & Securities. "Choi has been long-time finance ministry person and he basically spearheaded major economics policies of the Yoon administration from the very beginning so its a safe choice."

Currently, the ruling party controls only 37% in the 298-member parliament, compared with 56% or 168 seats held by the main opposition party.

Yoon doesn't need parliamentary approval to appoint a new finance minister, who also serves as deputy prime minister.

(Reporting by Soo-hyang Choi; Edting by Ed Davies)

By Cynthia Kim and Soo-hyang Choi