Many recent studies show that grassland biodiversity is linked to ecosystem functioning (BEF Theory) and to its capacity to deliver a large diversity of ecosystem services (ES). However, till now no methods allow an easy diagnosis of the level of ES produced, neither a concomitant evaluation of these services (i.e. forage production, biodiversity conservation and pollination or carbon sequestration). Our goal was to develop indicators of ES using botanical surveys (as a proxy of biodiversity), because botanical survey is quite easily accessible and is integrative of the spatiotemporal variability of grassland ecosystems. We used a multicriteria analysis tools to aggregate different criteria calculated from botanical survey to assess ES scores (ranged from 0 to 1). This tool used a set of indicators, which mixed academic knowledge and expertise. The first step was to develop a set of indicators (selection of the botanical survey criteria and the way to aggregate them) based on literature survey. Then, they were discussed with 20 experts during a workshop to produce a more finalized version of the indicators. 6 ES, i.e. forage production and quality, flexibility of forage production, nitrogen availability for vegetation, biodiversity conservation, resilience hazards and pollination, were selected.