Abstract: The use of land is the fundamental requirement of the rational use of land by local conditions. Given the mismatch of agricultural land resources, which is typified by the problem of garden land under the mountain and farmland on the hill, the promotion of the replacement of farmland with forests and gardens and the optimization of the spatial distribution of agricultural land is of great significance for the promotion of arable land preservation and sustainable use of farmland, and the scientific calculation of the potential of replacement of farmland with forests is the fundamental basis for this. The study takes Nanfeng County, Jiangxi Province as an example, and constructs a system of evaluation indexes of arable land suitability from four aspects: land quality, geographical location, ecological conditions, and spatial pattern, and uses the four-quadrant method to measure the potential with slope and arable land suitability as the dominant factors. The results show that: 1) The suitability of farmland in the evaluation area is generally good, but the suitability level of local farmland is low, which makes it difficult to realize the best use of land; the arable nature of forests in the evaluation area is relatively poor, with the arable nature of Class IV and Class V forests accounting for 65.39 per cent of the evaluation area; the arable nature of fields in the evaluation area is relatively good, with the arable nature of Class Ⅰ, Class Ⅱ and Class Ⅲ fields accounting for 84.73 per cent of the evaluation area; and the conditions of agricultural production are favorable, but some of the fields have poor arable land, which makes it difficult to develop and utilize them. 2) The potential for replacement with farmland and the potential for replacement with forest are unevenly distributed. Specifically, the potential for replacement with farmland total of 15,437.86 hm², of which 6,548.17 hm² was forest land under the mountain and 8,889.69 hm² was field under the hill; The total potential of forest land to be replaced is 778.91 hm², of which 69.70 hm² is farmland on the‘mountain’and 709.21 hm² is garden land on the‘mountain’to be adjusted. 3) The replacement potential shows obvious spatial differentiation. Among them, the potential suitability for replacement with farmland is mainly distributed in Sangtian Township, Baishe Township and Laixi Township, which are mainly concentrated in the central Valley plain; the potential suitability for replacement with the forest is mainly distributed in the hilly and mountainous areas of Fufang Township, Sanshi Township, Taihe Township and Zixiao Township, which are more in east and west and less in the center as a whole. 4) It is recommended that differentiated promotion strategies be formulated based on different land-type adjustment scenarios, on the premise of adapting to local conditions and prudent promotion. This study differs from the past potential measurement based on suitability evaluation by constructing a potential identification mechanism for farmland, forest and field replacement that combines slope and farm ability, identifying the mismatch space of farmland, forest and field through slope, and screening replacement plots based on the results of farm ability evaluation, which can effectively clarify the direction, potential and path of optimizing the layout of agricultural land. However, this identification mechanism assesses the replacement potential of farmland, forests, and fields on a broader scale, necessitating further verification through field surveys and explorations. Additionally, the conversion of farmland into forests and gardens encounters various challenges, including inadequate policy support, conflicts over land ownership, unequal distribution of benefits, and low willingness among farmers. Relying solely on theoretical assessments of potential makes it difficult to achieve optimal adjustments in the layout of agricultural land.