sweet clover (Melilotus officinalis L.) is a legume species, widely used as a forage crop for herbivores. This study aimed to research the nutritional compositions of herbage and silage M. officinalis at vegetative, early flowering and full flowering stages. The crude protein (CP) and ash contents of M. officinalis herbages and silages in vegetative and early flowering stages were higher than those in the full flowering stage (P < 0.05). The linoleic and alpha-linolenic acid percentages in total fatty acids of M. officinalis herbages in vegetative and early flowering stages were greater than those in full flowering stage (P < 0.05). The neutral and acid detergent fibres without ash contents of M. officinalis herbages and silages at the full flowering stage were higher than those of vegetative and early flowering ones (P < 0.05). The malondialdehyde (MDA) concentrations (1.12–1.67 g/kg DM) of silages were higher than those (0.38–0.48 g/kg DM) of herbages. The in vitro gas production, metabolizable energy, net energy for lactation and organic matter digestibility values and the molarities of volatile acids in fermentation fluid of M. officinalis herbages were similar for all phenological stages (P > 0.05). The lactic acid contents of silages at vegetative and early flowering stages were higher than that of the full flowering one (P < 0.05). The linoleic acid contents of forages were negatively correlated with MDA forage content (P < 0.05). Consequently, the values of CP, alpha-linolenic acid and in vitro digestion for herbage, and the nutrient matter compositions of silage, in especially vegetative and early flowering stages, were at non-objectionable levels for quality forage. So, it is suggested that M. officinalis can be used as a good quality silage.