Productive paddy fields are an important asset in supporting food security. However, due to the increasing competition for land use with sectors outside agriculture, it has triggered the pace of land conversion without control and has the potential to threaten the stability of food supply itself. This study aims to identify the rate of paddy field conversion that occurs in Aceh Besar Regency, Aceh Province, Indonesia. This research was conducted through a spatial approach using the application of Geographic Information Systems (GIS) to identify forms of spatial change based on land use. The method used is a Supervised Classification. The results of the study showed that the highest rate of paddy field conversion occurred in the period 2010-2020 reaching 0.947%/year. This is not comparable to the ability of the substitution efforts made in the previous ten years (2000-2010) which was 0.88 %/year. The form of land conversion that occurred was dominated by the non-agricultural sector, especially residential needs reaching 61.89%. This has the opportunity to reduce rice production by 1,051.38 / year. Therefore, efforts to control the rate of land conversion are absolutely necessary to ensure sustainable food security.