Wetland stability plays a vital role in the structure and functions of wetland ecosystems. In order to study the regional change in wetland patch stability and the space-time dynamic of the marshes, an expert evaluation method was used to construct a wetland patch stability model at the patch scale. Sensing image data were collected to investigate the space-time changes to marshes patch stability in the Xianghai National Nature Reserve and its surrounding area between 1985 and 2015. The results suggested that between 1985 and 2015, the marsh patch stability characteristics were strongest in the central areas, weakest in the east, and relatively stronger in the west. Marsh patch stability was skewed towards the east, and the spatial centralization increased in the study area between 1985 and 2015. Furthermore, marsh patch stability gradually increased, its spatial structure weakened, and measures of dispersion increased between 1985 and 2015. Marsh patch stability has gradually decreased from the core area to the periphery since 1985 and marsh patch stability was greater in the experimental zone than in the buffer zones in 2015. This study provides practical suggestions that will improve marsh planning and management in the Xianghai National Nature Reserve and its surrounding area.