Abstract: Variations in the chemical composition and biological activities of a functional food Sphallerocarpus gracilis stems and leaves (SLSG) harvested at different time were investigated, so as to provide new information and scientific recommendations with the best biological activities for the further exploitation of this resource. The samples harvested in autumn in autumn showed higher contents of most nutrients than harvested in spring, and the samples harvested in the second year showed higher contents of most nutrients than harvested in the first year. Following in vitro GI digestion, SLSG showed a good release percentage for most elements; however, the release of amino acids, especially Trp, Gly, Pro and Glu, which showed a very low release percentage (approximately 6%～11%). Regarding polyphenols, L7G and A7O were the main phenolic substances in SLSG, and 48%～55% of TP and 40%～70% of the individual phenolic substances were observed in the serum fraction. SLSG showed a good antioxidant capacity, an inhibitory effect against α-glucosidase and a hepatoprotective effect in vitro. Polyphenols and amino acids were the main contributors to these biological activities. Harvesting time T4 showed the best results in most indexes, including contents of Ca, Zn, Cu, Se Na, P, polyphenols, antioxidant ability, inhibitory effects on α-amylase and α-glucosidase, etc. These results increased the understanding of the chemical composition and biological activities of SLSG and provided new information and scientific recommendations with the best biological activities for the further exploitation of this resource.