A healthy ecosystem is the basis to guarantee efficient ecological services. Under the increasing anthropogenic disturbance island ecosystems tend to be more vulnerable after the construction of sea-cross bridges, which influence ecosystem services. Based on the Island Ecological Vulnerability Index (IEVI), a new index was formulated to assess island ecosystem service value of Zhujiajian Island (Zhejiang province, China) in 2015. This index is called Ecosystem service value adjusted with ecological vulnerability (AESV). The change of AESV in the next 20 years is forecasted based on the simulation of land use and IEVI during the research period. The main results of this study are: 1) Forest ecosystem services are most influenced by ecological vulnerability among all ecosystem types. The ecosystem service value of forests in 20 years estimated by the AESV method is 17% lower than the value estimated by the traditional method. 2) Forests, which accounts for 45% of the island area, supply 2/3 of the total ecosystem service value of the island, while the remaining ecosystem services are mainly provided by wetlands. 3) In the next 20 years, the value of ecosystem services will decrease rapidly under the pressure of land use change and the increase of IEVI. Compared with 2015, the AESV of the whole island in 2035 will decrease by 37%. The assessment of island ecosystem services adjusted with ecological vulnerability can improve the accuracy of the evaluation of services provided by an island ecosystem, and eventually provide a basis for the ecosystem management of vulnerable island ecosystems undergoing land use change such as occurs following their connection to the mainland via sea-cross bridges.