In 1960, he also graduated from the Academy of Social Sciences of the Communist Party of the Soviet Union in Moscow.

He joined the Communist Party of Germany and became a member of the Oschatz District Anti-Fascist Youth Committee.

Upon returning to East Germany in 1960, Eichler worked as a personal assistant for Walter Ulbricht until 1971.

He succeeded Otto Gotsche as the Secretary of the State Council in 1971 and served in this position until November 16, 1989.

On January 3, 1990, Eichler was summoned for a hearing by the interim Volkskammer Committee to review cases of abuse of office, corruption, personal gain and other acts suspected of violating the law and questioned about the former Schorfheide special hunting area.