Rice is the most important food crop in China, which is also the most water-intensive crop. Yunnan Province in China, located in the southwestern plateau, has a large area of mountainous dryland and is very short of irrigable rice fields. Consequently, farmers in mountainous areas purchase rice from the market. This study leveraged the seasonal coincidence of rainfall and heat from April to October, adopted rainfed dryland direct seeded cultivation technology, and evaluated the adaptability and yield stability of rice varieties in the mountainous drylands in Kunming, the province. In addition, based on climatic and topographic factors relevant to rainfed dryland rice cultivation, Geographic Information System (GIS) technology was applied to assess the suitability of areas for dryland cultivation and predict the extent of suitable areas and potential rice production. The objective was to improve food security and reduce poverty in these mountainous regions. Results showed that among the 30 tested japonica rice varieties, only three varieties were suitable for rainfed dryland cultivation, while about 90.0% were unsuitable. The high-quality variety Dianheyou 615 was identified as suitable and was demonstrated over two consecutive years in five villages across three counties in Kunming's mountainous drylands. The total demonstration area covers 59.94 ha, with an average grain yield of 7.58 t/ha, which produced 5.25 t/ha of polished rice. Based on an average annual per capita consumption of 125.0 kg of polished rice, 1 ha could meet the annual rice needs of 42 individuals. GIS analysis indicated that 4.15 & times; 104 ha of land was suitable for rainfed rice cultivation, accounting for 1.97% of the total arable land of Kunming. These rainfed drylands could produce 21.79 & times; 104 t of polished rice annually, sufficient to supply 1.74 million mountain residents. The findings provide a technical basis for realizing the production potential of rice farming in mountainous rainfed drylands, thereby strengthening rice security and contributing to poverty alleviation among mountain farming communities.