Cerithium zonatum is a dominate species in an intertidal zone of Shi-Lang, Green Island. This study aimed to characterize the population dynamics, reproduction and trophic ecology of C. zonatum in this intertidal zone. Results indicated C. zonatum in rocky habitat had high density, high growth rate and small shell length. In seagrass bed it was low in population density and large in shell length. The reproductive season of C. zonatum was from spring to summer, with indirect development and short planktonic period. The C. zonatum was a primary consumer with £_13C values of -6.97 - -6.26‰ and £_15N values of 3.65 - 5.13‰. They fed on seagrass detritus and periphyton including microalgae and filamentous green algae. The major food was seagrass detritus and filamentous green algae in the seagrass beds. In the rocky and sand habitats, the major food was microalgae and filamentous green algae. The population dynamics and food sources of C. zonatum were different among seagrass bed, rocky and sand habitats. In general, the C. zonatum was an opportunistic feeder with low mobility. And, the high population density and growth rate of C. zonatum in rocky habitat might result from abundant food sources in the area.