Diversity of parasitoids species remains questioning in several ecosystems poorly surveyed. The present study is focused on dipteran parasitoids species infecting orthopteran in forest-steppe ecosystem of Mongolia. Among a total of 420 hosts from four species, 20 were found to be infected and 200 larvae of dipteran parasitoids recovered. Genetic studies on a subset of larvae shows the presence of up to seven taxa whose none is represented in databases (although 13 species were previously reported in Mongolia), indicating a large and unexplored diversity of dipteran parasitoid in Mongolia. Further studies will be focused in establishing of this diversity and the determination of the species.