The research presented in this paper aims to analyze demand-supply and local policy of food security and school lunch system in Mae Rim District, Chiang Mai Province, based on the concept of participatory action research (PAR). Data was collected from 574 school administrators, teachers in charge of school lunch program, parents and students, 1362 farmers, and 85 local administrative officers, community leaders and key informants, by questionnaires, in-depth interviews, focus group discussion and participatory assessment of activity-based learning outcome. The results showed that; 1) Total demand of agriculture products for lunch ingredients was only 37%, such as rice, vegetables, fruits, and eggs, produced by local farmers. The management process of school lunch services based on government regulations framework, especially procurement and school lunch budget (20 baht) per person per day, that’s difficult for selecting quality raw materials and increasing nutrition or essential nutrients for school-age children. 2) Mae Rim district had enough farmland for food crop production and food security, especially rice, the most production (64.3%), vegetables-herbs and fruits (20.7%) but organic agriculture production is only14 percent of total farming. 3) The most concern in blood testing of 400 cases, from 245 farmers and 155 students, found that only 14.8 % were in normal and safe levels but 55.5% in risk and 29.7% unsafe, indicating the health risk of farmers and school-age children that needs to be monitored, followed up, and changes their consumption behavior.