Throughout the film's long development Luise Rainer, Margo, Maureen O'Hara, Kim Hunter, and Claudette Colbert were all considered for the female lead and Paul Henreid was considered for the male lead. At one point, David Hempstead was to produce.
China Sky (1945) had a long and difficult gestation. RKO bought the rights to Pearl S. Buck's story in September of 1941. In a New York Times article, producer Maurice Geraghty stated that one reason for the film's troubled production history was the studio's opposition to an unsympathetic anti-American Chinese character. By mid-March of 1944, five months before the start of production, the doctor's nationality had been changed to Japanese-Korean and his name changed to Kim.
According to the date on the telegram Dr. Durand receives near the beginning of the film, this story starts in October of 1938.
According to film scholar Hye Seung Chung in her book "Hollywood Asian"; the character of Dr. Kim (played by Korean-American actor Philip Ahn), is notable as very first self-identifying Korean character in a Hollywood film.