The paper presents an approach for the metamorphic viruses detection based on its obfuscation features analysis. The obfuscation features were obtained on the basis of the equivalent functional block search in the suspicious program and its modified version. The results of the research demonstrated that the efficiency of metamorphic viruses detection based on the proposed obfuscation quantitative features depends on the choice of the similarity metric at the stages of the search and the choice refinement of the equivalent functional blocks. The adequate choice of similarity metrics at both stages allowed increasing the detection efficiency of the metamorphic viruses.