Abstract: The landscape pattern indexes were usually used to analyze the spatial structure characteristics of mangrove landscape, as the mangrove is a kind of special forest distributing only in the intertidal zone. Its ecological system is much different from the land ecological system in terms of function and role, the exchange mechanism of matter and energy, and so on. Therefore, it is necessary to develop a suitable method for analyzing its spatial structure in landscape level. In this paper, the Pearl bay, Maoweihai bay and Tieshangang bay in Guangxi were used as the study sites. We discussed the ideal distribution of mangrove within a bay or gulf by considering their function and role, especially their function of wave reduction and coastal protection.Four indexes were defined for analyzing their spatial structure in landscape level, including abundance of mangrove(AM,c_AM), evenness of mangrove distribution(EMD,c_EMD), ratio of mangrove coastline length to the total coastline length(RMCL,r_RMCL), and ratio of area of high efficiency coastal protection mangrove to the total area of mangrove(RAHP,r_RAHP). Then their calculation methods were developed based on the spatial overlay of maps of mangrove distribution and coastline. These four indexes related not only to the area and patch-number of mangrove, but also to their distribution state(patch location, shape and size)as well as the length and spatial position of coastline. With explicit physical meanings, they reflected the spatial structure of mangroves in a gulf or bay. These four indexes could not only be used for comparing the spatial structure of mangrove landscape of different bays in the same period, but also be used for analyzing the dynamic of spatial structure of mangrove landscape of the same bay in different period, and would be helpful for optimizing the spatial structure of mangrove landscape. Finally, the Pearl bay, Maoweihai bay and Tieshangang bay in Guangxi were used as the study sites for an empirical research.