Abstract Large-scale artificial forests have replaced original land cover types such as arable land, garden land, evergreen broad-leaved forest, and Pinus khasya forest. In particular, the widespread introduction of Eucalyptus has caused great changes in land-use patterns and affected ecosystem service functions. How to rationally allocate land, improve the land utilization rate, and ecosystem service functions in a limited land area have become research hotspots. This paper mainly studies the land-use optimization in Lancang County, a large-scale eucalyptus-introduced region, by using the gray multiobjective dynamic programming (GMDP) model and the ant colony optimization (ACO) algorithm. The maximization of social, economic, and ecological benefits is used as the quantitative structure optimization objective in this model, while land-use suitability and spatial compactness are used as the spatial optimization rules. The results show the following: (1) The economic and ecological benefits are significantly improved after optimization compared with those of the current situation and the integrated land-use planning in Lancang County (i.e., the overall plan hereafter or the overall planning of land use by government departments). The social benefits are lower than those in the current situation and overall plan. (2) The suitability of the land-use spatial structure after optimization is improved to some extent compared with the land-use structures of the current situation and overall plan. In particular, the suitability of urban construction land is significantly improved after optimization. (3) The patch density (PD) index of each land-use type is significantly reduced after optimization. The fractal dimension (FRAC) indexes of urban construction land and natural reserves are increased compared with those in the current situation and in the overall plan. The compactness index (CI) of land use increases after optimization, and the degree of land-use fragmentation is improved significantly. (4) Land transfer is greater for arable land, garden land, forests, and natural reserves after optimization. Compared with the overall plan, more high-quality arable land and forest resources may be protected. In conclusion, optimized land use is conducive to promoting the rational use of land resources, socioeconomic development, and environmental protection in eucalyptus-introduced regions.