Abstract: The community stability of different legume-grass mixes has been analysed using the fuzzy synthetic evaluation method. Onobrychis viciaefolia, Medicago sativa, Trifolium pratense, Dactylis glomerata, Bromus inermis and Phleum pratense were used in four different combinations (3, 4, 5 or 6 species in each mixture) at three sowing ratios of legume to grass (5∶5, 4∶6 and 3∶7). In order to measure community stability and susceptibility to invasion, seven indexes (including the relative densities of grasses and legumes, the yields of forage, crude protein, ether extract, neutral detergent fiber, and the relative total yield) were analysed from 2008 to 2012. The component stability of legumes in mixtures with O. viciaefolia was lower than that of grass, while it was higher in mixtures that did not contain O. viciaefolia. Community stability increased with increases in species diversity. Stability was lower in the 4∶6 legume-grass mix than at other ratios. Susceptibility to invasion was higher at 5∶5 than at other ratios and was minimally affected by species diversity in the various mixes. Fuzzy synthetic evaluation showed that stability at 4∶6 was lower than at other ratios and that stability was rarely affected by species diversity. In conclusion, the study suggests that species diversity and the ratio of legumes to grass may affect some rather than all aspects of community stability. Further research is needed at appropriate time and space scales and using standardized indices to discover what other factors are influencing the stability of legume-grass mixes.