Since 1997, Costanza and others assessed the value of global ecosystem services. The assessment methodology and the adaptability of the established methods have become the concern of academia. The paper assesses the four forest ecosystem services of Beibu Gulf in China, based on the services valuation methods, accepted by civil experts. These services include forest products, carbon sequestration and oxygen release, water conservation and biodiversity maintenance. The assessment results showed that those forest ecosystem services approximates to 296,025,000,000 Yuan. The study found that the method this paper utilized to assess the biodiversity maintenance may not reflect the real potential value.