This paper took mangrove wetland of Bamen port in Wenchang of Hainan Province as the area of research. Six period remote sensing images, including the 50-year period (1964, 1972, 1988, 2000, 2009, 2015), were used as the main data source to establish the regional landscape database and analyze the landscape dynamic changes of the study area, using a land transfer matrix and 10 kinds of relevant landscape indices. The results showed that (1) the built-up and surface areas of the raising water in Bamen port increased by 7.72% and 12.55%, respectively, from 1964-2015. At the same time, the proportions of the cultivated, forest, and mangrove areas decreased by 7.01%, 9.16%, and 9.74%, respectively. (2) The number of plaques in the study area increased to 685, the average patch area was reduced by 39.12%, the degree of polymerization decreased by 3.5%, the largest patch area decreased by 28.38%, and the CONTAG decreased by 9.26% from 1964 to 2015. During the same period, the mean patch-shape fragmentation index and area-weighted average patch-shape fragmentation index increased by 0.0148 and 0.0207, respectively, and the plaque density increased from 0.0653/hm² in 1964 to 0.1073/hm² in 2015. (3) The relationship between the land use/cover changes and their surrounding lands and landscape fragmentation in Bamen port mangrove wetland was mainly reflected in the influences of aquaculture water surface and construction land area on the study-area landscape fragmentation index. The influences of the changes of aquaculture water surface and construction land area on the landscape fragmentation process were mainly reflected in the degree of polymerization, number of plaques, and role of CONTAG. Among them, the influences of the changes in aquaculture water surface area on landscape fragmentation were mainly reflected in the encroachment of mangrove area. As a result, the proportion of the mangrove area accounting for the total research area decreased from 15% to 5.25%, and the mangrove forest showed a transformation from the large-area continuous concentration to the small-area isolated distribution. The influences of the changes in construction land area on landscape fragmentation were mainly reflected in the rapid development of the city and transportation facilities. The transformation of various types of mangrove swamps in Bamen port mainly embodied on that the mangrove areas were transformed into the aquaculture water, and the building area was converted from the woodland and cultivated land in the past 50 years. Thus, the primary reason for the fragmentation of mangrove wetland in Bamen port was the enhancement of human activity and the expanding scope of its influence.