Land ecological security (LES) assessment is a main focus of LES research. The aim of this study was to develop a dynamic approach to achieve an objective assessment. Su-Xi-Chang area was selected as the study area. Based on the source-sink landscape theory, ecological land and construction land were treated as the source and sink, respectively. The minimum cumulative resistance model was applied to simulate the dynamic changes of these landscapes. The resistance values of the ecological land were obtained from ecosystem service values of different land-use types, whereas those of the construction land were derived from ecological risk values. The spatial expansion and simultaneous invasion of both construction land and ecological land were simulated with ArcGIS software. In the case of ecological land expansion, three scenarios were simulated, i.e., low-, middle-, and high-level LES. In the case of construction land expansion, three urban development models were designed, i.e., metropolitan development in priority (MD), small and medium cities development in priority (SD), and all urban sources development in equilibrium (ED). In the case of invasion, nine scenarios were formed from the spatial overlapping of these two kinds of expansions and their respective scenarios. The study area was zoned into five levels of LES according to the invasion results, i.e., suitable construction (very low), ecologically fragile (low), buffer (middle), ecological security (high), and ecological core (very high) zones. The results of this study showed that:(a) Along with the scenarios of LES ranging from low- to high-level, the expansions of construction land in different development models displayed a significant convergence trend of spatial agglomeration; the modeling of ecological land, however, indicated a trend of circular sprawling from the core to the outward. In the low-level scenario, the percentage of suitable construction zoned land was the highest in the MD model, at 27.90%, and the lowest in the SD model, at 21.59%. In the high-level scenario, the percentage of suitable construction zoned land was the lowest in the MD model, at 9.42%, and the highest in the SD model, at 13.10%. (b) In the same ecological security scenario, the different urban development models displayed different impacts on construction land expansion. In the low-level scenario, the combined percentage of suitable construction zoned land and ecologically fragile zoned land was the lowest in the MD model, at 38.24%, and the highest in the SD model, at 46.03%. In the high-level scenario, the corresponding value was also the lowest in the MD model, at 14.41%, and the highest in the ED model, at 21.20%. (c) Urban development models have significant influence on the levels of LES. Among the three urban development models in this study, the MD model benefitted intensive land use and found the land to be suitable for rapid urbanization, improving the area's LES from the current level to a higher level. A LES zoning plan was recommended, as well as measures of land-use control. In the plan, the area percentages of the suitable construction, buffer, ecological security, and ecological core zones were 27.90%, 7.76%, 29.07%, and 35.27%, respectively. The developed approach was found to be effective in dynamically assessing LES and beneficial in the differential management of land resources. The dynamic approach investigated in this study highlights the methodology in the optimization of ecological land patterning. Finally, issues on how to improve this developed method and future research directions have also been discussed.