Menjangan island is part of the West Bali National Park, the physically including unique islands because has an area of 175 Ha, with no population and have equitable distribution of coral reefs around the island. Tourism is a major activity in this island. The exposure of coral reefs ecosystems exceslys without any limitation of activity will interfere with the coral reef ecosystems. This research is intended to find out some exposure elements and value of coral reefs ecosystems by tourism activities and natural elements that threat to damage the coral reefs. This reseach is focused on 4 points location snorkel using vulnerability theory approach with exposure parameters, the visitors number, density of Acanthaster planci, wave height, depth, pH, temperature, substrate type and tidal range. The result showed that exposure potential comes from various elements, i.e the natural elements and other elements such us the tourism activity. The exposure value of Menjangan island is 1.5 which is in low exposure level.