Marine species diversity maintenance service means that there are abundant living organisms in the sea, and moreover the sea provides important habitats, e.g. spawning grounds, overwintering grounds, feeding grounds and the shelters. Based on Contingent Valuation Method, a questionnaire survey on willingness-to-pay of local residents for the protection of marine species diversity was conducted in the towns around Luoyuan Bay in August, 2009, and thereby, marine species diversity maintenance service in Luoyuan Bay ecosystem was valuated. The average willingness-to-pay for 4 kinds of species was 618.8 yuan RMB per household in 2009. Marine species diversity maintenance service value of Luoyuan Bay was 7.47 million yuan RMB, 19.12 million yuan RMB, 25.65 million yuan RMB, 38.2192million yuan RMB, 52.7200 million yuan RMB from 2004 to 2008 rspectively. The annual household income, level of understanding of marine species diversity and environment awareness are the major factors in affecting marine species diversity maintenance service. For better protection of marine species diversity, both economic and environmental policies are necessary. The local government should pay more attention to how to balance and coordinate these two policies.