[1] Following the closure of Czech higher education during the German occupation of the country, he has gone to Slovakia, where he worked since 1938 at the Slovak Technical University in Bratislava.

Since 1940 he began to work at the same time on the Faculty of Natural Sciences of the Comenius University in the office of head of Geological and Paleontological Institute.

In 1952 Andrusov became head of Department of Geology at the Faculty of Natural Sciences at the Comenius University and remained in office until 1970.

The results of his research were summarized in a five volume monograph The Geological research of Klippen zone of the Western Carpathians (1931 - 1955), Apercu de la Géologie des Carpathes occidentales de la Slovauie centrale (1931), three volumes of The Geology of Czechoslovak Carpathians (1958 - 1965) and monograph Grundriss der Tektonik der Nördlichen Karpaten (1968),[3] which is considered one of the highlights of synthesis of the tectonic structure of the Western Carpathians based on the principles of the geosyncline theory.

In addition to scientific activities he also solved practical geological tasks related to construction of dams, railways, tunnels and searching for non-metallic deposits.