Son of Henry and Mary Ann Mark Killie, Charles Killie was born in Marshall, Illinois in 1857. After completing high school Killie obtained work first at a newspaper, then as railroad clerk and finally in the insurance business. In 1879 he married Louise Scott. In 1886, at the age of 29, Killie entered Princeton Seminary. Following his graduation in 1889 Killie and his wife applied and were accepted as itinerating missionaries for the PCUSA's Board of Foreign Missions.

Killie's first appointment was to the Shantung Mission at Ichou-fu. In 1899 he and his wife were transferred to the Peking Mission. Killie's work in Peking corresponded with the Boxer Rebellion in 1900 and he used that opportunity to report and photograph the events. As a result of his services during the siege of Peking, Killie was voted the bronze and gold medal of the Military Order of the Dragon by the U.S. Army and Navy officers. Killie left Peking in 1902 and was then transferred to Paoting-fu where he served until 1912. In 1912 he withdrew from the field in ill-health, and returned to the U.S. with his wife and spent the remainder of his years lecturing for the Board of Foreign Missions.