In view of the increasingly prominent conflict among agriculture, ecology and urban space in the central city, this paper drew inspiration from the Garden city theory, and proposed a method to refine the urban ecological security network by using the suburban high ecological value farmland, and to construct a coordinated and orderly territorial spatial pattern of "three living" spaces. We utilized remote sensing data, land surveys and socio-economic data from Fangchenggang City, and based on the comprehensive evaluation of the suburban farmland, assess its ecological value using the equivalent factor method, which was modified by the evaluation results. Further we applied InVEST, MSPA, and MCR models to construct a preliminary urban ecological security network, and then chose high ecological value farmland as temporary ecological nodes for network reconfiguration and conducted comparative analysis. Finally, we used the reconstructed new network to guide the optimization of planning zoning in the central city area, and explored the spatial control rules and joint management mechanisms for the two levels of ecological network elements in the city area and central urban area. The results showed that: (1) The ecological value of cultivated land per area in Fangchenggang urban area was 35540 Yuan/hm², and the high ecological value farmland was relatively evenly distributed around the city. (2) The reconstructed network had added 34 temporary nodes and 51 green belts, extended by 48.425 km, and added 808.89 hm² of ecological source land. (3) The new network can effectively guide the formation of a circle development structure in the central city, which had improved connectivity, effectiveness, and stability compared to the original network. The results provided new ideas for the optimization of regional spatial structure under the background of territorial spatial planning that emphasizes coordinated development.