Kai Kristiansen trained as a furniture maker and finished his apprenticeship in 1948.
Two years later he was accepted into the Academy of Fine Arts where he studied furniture design under Kaare Klint. In the mid 50’s he opened his own design office and collaborations with Schou Andersen for whom he designed the famous #42 dining chair, began.
During this period he also worked with Magnus Olesen on the sofa/chair series #121. Throughout his career he has been associated with some of the best known manufacturers, i.e. Kjærsgaard, Fritz Hansen, Tarm og Feldballe.
Kai Kristiansen was responsible for organizing a regional Furniture Fair from 1956 to 1965.
From 1966 to 1970 he was the driving force behind the Scandinavian Furniture Fair.