Three species of cone snails collected in the Coastal Central South of Vietnam represent three different feeding mode C. striatus (eating fish), C. textile (eating molluscs) and C. vexillum (eating polychate) showed differences in morphological parameters, the relationship between different parts of venom ducts and radular teeth structure. Results showed that fish eaters have larger volume of venom duct, radular teach with more branches than the other two species. This can be concluded that the venom ducts of three species of Conus snails have close relationships with the feeding mode.