：Delineation of urban growth boundary is an important means to prevent the disorderly spread of urban land, protect the ecological environment of the open space outside the cities, and realize the smart growth of cities, which is of great significance to the healthy and sustainable development of cities. Currently, the studies on urban growth boundary delineation mostly use model method, such as Cellular Automata (CA) model, a relatively mature model, to simulate future urban patterns. However, these studies mostly focuses on the delineation of urban growth boundary. There is little effort on quantitative delineation of the inertia boundary of urban growth. The delineation of inertial boundaries can not only reserve a certain space for urban development, but also improve implementation efficiency in urban planning. Based on this, we proposed a method based on the kinetic energy theorem of the mechanics. The FLUS model and the Morphological Erosion and Dilation method (MED) were used to delineate the urban growth boundary. Slope and land use type were used as the frictional force to delimit the inertial boundary. The FLUS model inherits the Artificial Neural Network (ANN) and the Cellular Automaton(CA) model for simulating and predicting the future urban landscape. The MED was used for the clustering of urban neighborhoods to merge into a single area, while eliminating small but isolated urban plaque. In our paper, we selected Fuzhou, a coastal developed city with obvious changes in recent years, as the study area. We simulated the land use patterns from 2000 to 2015 to verify the accuracy of the model. The overall accuracy of land use simulation in 2015 was 0.9389 and the Kappa coefficient was 0.9165. We further predicted the land use pattern in 2027, and delineated the urban growth boundary and inertia boundary in 2027. Results show that the FLUS model and MED can effectively simulate land use and better fit the growth boundary of urban land use. Using the method of kinetic energy theorem for reference, the inertia boundary of a city can be well delineated according to the expansion resistance in different directions and the expansion intensity in different directions, which provides practical operability and reference values for future study.