Abstarct: Food security is the first principle for maintaining the health of people in society, so that people can play a key role in political, economic, social and cultural development. On the other hand, trade openness is very important for promoting the economic growth of countries. Trade openness can have different consequences for countries' food security, and these consequences need to be assessed and anticipated. Therefore, the main purpose of this study was to investigate the impact of trade liberalization on food security in ECO member countries. The reason for choosing ECO countries to study is that these countries are very close economically, culturally and geographically. It also intends to cooperate economically with each other in the form of ECO. The study period covers the years 2000-2019. Two indicators were used to measure food security: 1- The ratio of food exports to food imports, which shows the dimension of food self-reliance, 2- Production of agricultural products, which shows the dimension of food access. So two models were estimated. In the first and second models, respectively, the trade balance index of food and agricultural products are dependent variables. In all models, the explanatory variables include trade openness, per capita income and price index. The required data were obtained from the World Bank website. Each model was estimated by three well-known methods of panel data estimation, namely Pooled regression, fixed effects and random effects, and finally the appropriate and final model was selected using F-Leamer and Hausman tests. The results showed that in terms of food self-reliance, trade openness and per capita income have a positive effect and price index, has a negative effect on food security. In terms of access to food, trade openness has a negative impact, and per capita income and price index have a positive impact on food security.