Discussed the antioxidant and antimicrobial activities in vitro of different polarity parts in longan seeds, and effective parts were selected. The total polyphenol contents and the antioxidant activities of different polarity parts in 95% ethanol extract from longan seeds were determined by Folin-Ciocalteu method and ABTS assay, DPPH assay, pyrogallol autoxidation assay and phenanthroline-Fe²⁺ reaction system, respectively. Meanwhile, their antibacterial activities were evaluated by oxford-cup method. The results showed that the ethyl acetate extract had the highest content of total polyphenols, which was (693.51±9.52) mg/g among the four extracts. The four extracts had a relatively weak scavenging effect on superoxide anion radicals but could strongly scavenge ABTS and DPPH and hydroxyl free radicals, The antioxidation activities in the order of ethyl acetate extract > chloroform extract > n-butanol extract > water residue. The four extracts had inhibitory effects of different intensity to Salmonella, Escherichia coli, Staphylococcus aureus, and the ethyl acetate extract was especially outstanding, except for the water residue on the inhibition of Salmonella and Escherichia Coli had no obvious effect. According to the above results, the ethyl acetate extract of longan seeds could be regarded as a kind of good natural antioxidant and bacteriostatic because of it is rich in polyphenol compounds, and with a great pharmaceutical value and profound prospect.