Biodiversity is declining at an unprecedented rate. Many grassland species have been lost and are now of conservation concern. Identifying efficient biodiversity indicators is a key pillar of the global conservation strategy. Mongolian Lark (Melanocorypha mongolica) is a charismatic bird species abound in Mongolian steppes, and recent studies demonstrated that this species share similar habitat requirements and likely co-occur with other grassland birds. We tested the hypothesis that Mongolian Lark would make a suitable indicator for different aspects of avian biodiversity. We made a large-scale bird survey in Inner Mongolia, and classified point counts into three groups based on different taxonomic, functional, and phylogenetic biodiversity measures. We identified species indicators of each group using the indicator value (IndVal) analysis, and examined the bird compositional difference among groups. Linear models were used for studying the patterns of occurrence of Mongolian Lark in relation to various biodiversity measures. Mongolian Lark showed the highest indicator value in comparison with other potential species indicators. Bird species richness is significantly higher at sites with Mongolian Lark, and its occurrence was negatively correlated with species abundance, functional richness, Rao's quadratic entropy and phylogenetic diversity. Mongolian Lark is therefore a suitable indicator species for avian biodiversity in Mongolian steppes. It is highly distinctive in flight and usually seen singly. The widespread distribution and charismatic appearance make it easy to monitor and adequate for citizen science, and may provide useful information on the paradigm of surrogacy in conservation ecology.