At this time, he met Seong Hon, who would become a lifelong friend, and due to this influence, He joined the Westerners when the Bungdang was formed later.

In 1558, he passed the regular triennial civil service examination (식년문과) as a seventh place and started his governmental career at the Office of Diplomatic Correspondence (승문원).

Afterwards, he went through the Editorial Examiners of the Office of Royal Decrees (예문관검열), the proofreader (정자) and first copyist (저작) of the Office of Special Advisors (홍문관), and became Assistant Section Chief of the Ministry of Military Affairs (병조좌랑) in 1561, Assistant Section Chief of the Ministry of Personnel (이조좌랑) in 1562.

After finished the task, he was raised to the Grand Master of Comprehensive Governance (통정대부) and also appointed as the head of the Five Guards (오위장).

In doing so, Yun du-su stabilized the situation considered unstable and suspected that the king did not have a crown prince to die after.

[6][7] In 1575, due to the conflict between Sim Ui-gyeom and Gim Hyo-won over the appointment of Section Chief of the Ministry of Personnel, Sarim was divided into the Easterners and the Westerners.

[2] As Inspector General (대사헌) Gim Gye-hwi requested, Yoon Doo-soo was appointed again and became Magistrate of Yeonan Strategic Prefecture (연안도호부사).

[4] In 1588, Yun Du-su became second deputy directors of Privy Council (동지중추부사) in June and governor of Pyeongan Province (평안도관찰사) and magistrate of Pyongyang Magistracy (평안부윤) in autumn.

[3] In March 1591, he became the Minister of Taxation, but in June, He had decided to support Prince Shinseong with Yi San-hae, but he supported Gwanghaegun in the Geonjeo issue, a partisan fight between the Easterners and the Westerners, so King Seonjo was angry and divested Yun Du-su of his office and exiled him with his younger brother Yun Geun-su to Hoeryong.

[3] On April 28, it was reported that Sin Rip had been defeated in Chungju, so King Seonjo proposed royal flight from the palace and it was decided the next day.

Yun Doo-su joined King Seonjo's departure to the west at the dawn of April 30 as an official holding sinecure post.

Arriving in Kaesong on May 1, the procession of the royal carriage took Yun Doo-su as the captain of Office of the Directorate General (어영대장) on May 2 and sacrificed to Right State Councilor the next day.

[8][9] Yun Doo-su insisted on sending an address to Liaodong to announce the war, punishing those who did not come with king as court officials, and remaining in Kaesong and defending.

Accordingly, Yun Du-su sent the governor of Hwanghae to soothe people so that the procession could leave Kaesong safely.

King Seonjo refused to accept this and asked to discuss the next destination, and Yun Du-su recommended going to Uiju rather than Hamhung.