After the Second World War, he was from 1947 CEO of the Chamber of Commerce Borna, an office he held until 1952.
In 1949, he became a member of the Christian Democratic Union (East Germany) (CDU) in which he was the Organization Secretary from 1952 to 1954 and Deputy Chairman of the District Association of Leipzig.
From 1958 to 1990 he was member of the parliament of the German Democratic Republic, 1963-1989 Chairman of the CDU faction, since 1971, Chairman of the Committee on Foreign Affairs from 1976 to November 1989 Member of the Bureau the People's Chamber.
In 1977, he was awarded an honorary Clasp to the Patriotic Order of Merit in gold.
In late 1989, due to a heart attack, Heyl resigned from his offices.