The services of ecosystem are critical to human existence and prosperity, providing necessary ecological products for human production and life as well as indispensable natural conditions for life system. The Natural Mangrove Reserve in Zhangjiang River Estuary is one of the most important National Natural Mangrove Reserve in China. Its environment has been degrading during the past decades for people neglecting the ecosystem services function value which is hard to currency turn. Thus, it is necessary to monitor and assess the Mangrove Reserve's dynamics, both to gain a better understanding of their basic biology and to help guide conservation and restoration efforts. Using Landsat TM/ETM+ Satellite data acquired in 1989, 1992, 1998, 2001 and an Aster image from the year 2003, the land use of the Reserve and its environment were extracted adopting the supervised Maximum Likelihood Classification Algorithm. The changes of land use and ecosystem services value were analyzed using Costanza's method of evaluating the global ecosystem service values. The total value change of ecosystem services in the study area per year are 2945.95×104$, 2861.74×104$, 2904.05×104$, 2794.67×104$, 2730.82×104$ respectively during the four periods (1989-1992, 1992-1998, 1998-2001, 2001-2003). The ecosystem services value change has a close relationship with W&B, population, build-up and forest. The results indicate that the ecosystem services value in the study area has been constantly deteriorating due to the human activities imposed on it, which is highly associated with the local expanding of build-up and brackish water fishponds all the while. And the downward trend of the ecosystem services value has become even more acute, with the development of the local economy.