After his secondary education Loch was drafted for military service in 1917. From 1918 to 1923 he studied law at the Universities of Cologne and Bonn and then worked as a legal adviser and tax counsellor. In 1936 he emigrated to the Netherlands, but returned to Germany in 1938 and from 1939 to 1945 was a soldier of the Wehrmacht.
In 1945 Loch was a co-founder of the Liberal Democratic Party in the district of Gotha. From 1947 he was Chairman of the municipal policy subcommittee of the Central Board, and from 1949 deputy chairman of the party. In 1951 he became party chairman, first jointly with Karl Hamann, and then alone, following the arrest of the latter in December 1952.
From 1946 to 1948 he was mayor of Gotha, then until 1950 Minister of Justice of Thuringia, and then till 1955 Minister of Finance of the GDR. As finance minister, he was a member of the Council of Ministers. From 1949 he was a member of the (provisional) Volkskammer (People's Chamber), from 1950 Vice Chairman of the Council of Ministers and from 1954 a member of the Presidium of the National Council of the National Front.
