For the last decade, a considerable number of informal environmental education facilities and institutions had been proposed and materialized in Korea. These valuable places were intended to provide all citizens with more exciting and experience-based learning opportunities, basically distinguished from formal, school environmental education. This study was aimed to device the process or preliminary model for developing an education program of informal environmental education institutions which are newly developed, intended for all age groups as life-long learning and relatively large scale in space and budget. The conceptual programming model was compared to and integrated with other education program development strategies which had been proposed in a variety of informal education contexts, and finally applied to the process for developing an education program of the National Ecological Institute. The results indicated that the proposed process seemed to be useful in constructing the whole frame for the education program and further effectively dealing with many kinds of possible problems and issues, especially for all levels of visiting groups, with different interest groups, and in the consideration of local contexts.