He was born on 21 September 1904 in the village of Skrinjano, Kyustendil Municipality. He graduated high school in Kyustendil (1928). During his school years he started painting caricature for various newspapers and magazines - "Red laugh", "Zvanar", "Echo" and others. These cartoons are signed with the pseudonym Proletarche.
He graduated painting at the Academy of Arts in Sofia under Prof. B. Mitov, Prof. Stefan Ivanov and Prof. Dimitar Gyudzhenov (1931). Already in his early creative years he became widely popular. His works are mainly in painting, but he also draws graphics and cartoons.
In the 1930s he was an illustrator of the newspaper ""Merry Band" with editor Emil Koralov and Lachezar Stanchev.
The first exhibitions in which he took part were in the 1930s. In the exhibitions participated with the sculpture Ivan Funev. He has been held accountable for his anti-fascist ideas in several of his works. Other main themes in Stoyan Vennev's paintings are folk folklore and lifestyle.
After September 9, 1944, he published numerous cartoons in the newspapers "Stirchell", "Workers" Delo" and others. His paintings also have great successes.
He organized solo exhibitions in Sofia (1942), Moscow (1965), GDR (1969), West Berlin (1971) and others. He participated in joint art exhibitions in the USSR, Czechoslovakia, China, Berlin, Budapest, Leipzig, London, Paris, Vienna, Athens, Bucharest, New York, etc. Аnniversary exhibitions: in Sofia (1954, 1964 and 1974) and Kyustendil (1984).
Stoyan Vennev's works are at the National Gallery of Art, the Art Gallery, the Dresden Gallery, the Pushkin Museum in Moscow, galleries in London, Paris, Chisinau, St. Petersburg and many private collections.
In 1950 and 1953 he was awarded the Dimitrov Prize.
Honored by the Honorary Citizen of Kyustendil in 1965
He died on March 20, 1989.