Abstract: The objective of this study was to contrast the effect of chitosan diguanidinylated (CSG) which derived from chitosan coating on Dimocarpus longan Lour.with chitosan (CTS) .Effect of CSG coating in extending shelf life of longan fruits, maintaining their quality and the antifungal activity of Lasiodiplodia theobromae and Colletotrichum gloeosporioides Penz.were investigated.The longan were dipped in aqueous solutions of 1% chitosan, 0.2%, 0.5%, and 1% CSG, respectively, and followed by draining, and packaged in commercial perforated plastic baskets and stored at (28±2) ℃ for 5d.Changes in ion leakage, malonaldehyde (MDA) , mass loss, ascorbic acid, total soluble solids (TSS) , titratable acid (TA) , and decay rate were measured.The result showed that coating with 1% CSG had a significant effect on maintaining fruit quality and decreasing fruit decay.CSG could completely inhibit the growth of Lasiodiplodia theobromae at 4mg/mL and had a good antifungal activity against Colletotrichum gloeosporioides Penz.at concentrations of more than 1mg/mL.