Kiril Donchev graduated from the State Academy of Music in 1959. He conducted a wind orchestra in Burgas (1959-62). Since 1962 he has mainly composed theatre and film music. He is among the leading Bulgarian composers whose names are connected with this genre. He worked as conductor and composer at the Bulgarian Army Theatre (1962-71), the Sofia Theatre (1972-88). In 1989 he was appointed composer at the Ivan Vazov National Theatre. He wrote music for most Bulgarian theatres. He composed stage music to performances in Moscow, Warsaw, Berlin, Prague, etc. He is member of the Union of Bulgarian Film Makers and the Union of Bulgarian Actors.

He wrote the music to over 240 theatre productions, 65 feature films, 30 documentaries, etc. His music was awarded at the international festivals in Venice (Italy), Girona (Spain), Essen (Germany), the Varna International Cinema Festival, the Plovdiv Cinema Festival, etc. It was also awarded by the Union of Bulgarian Composers, the Union of Bulgarian Film Makers, etc.