The objectives of this qualitative research aimed to study :) the phenomenon and guidelines on the excellent School Administration of Middle Secondary School Size Under the Secondary Educational Service Area Office 25 : A Case Study of Waengyaiwittayakhom School. The key informants were the 1 director, 1 vice director, 10 teachers, 5 school committee, 5 parents and 5 students representatives, a totally of 27 persons. The instruments were semi-structured interview, documentary study, fields study, in-depth interviews, participatory and non-participatory observation, field notes, records and photography. Data analysis using content analysis, data validation by triangulation method The results: 1. The phenomenon on school excellent administration at Waengyaiwittayakhom school were as followings: 1.1) The organization: The school of set policies to support the continuous development of educational quality standard sustainability. 1.2) The Strategic Planning: The school planning systematically set by using analyzing SWOT analysis for implementing continuously. 1.3) Focus on learners: Managing by listening to the opinions of stakeholders, especially from the learners, focusing on high participation in order to improve quality and school strategy. 1.4) Analytical Measurement and knowledge administrator: The school has an educational evaluation system using the quality assurance system for improving learning management. 1.5) The Staffing: The school promotes the teachers potential and personnel development by focusing on personnel evaluation in accordance with the education standards of the school and the ministry. 1.6) Focus on Operations: The school have systems and mechanisms to achieve their objectives by integrating the philosophy of sufficiency economy of the King Bhumibol Adulyadej in all activities. 1.7) The Outcomes: The school has developed all aspects for excellence and management to succeed systematically. 2. The guidelines on the excellent of administration at Waengyaiwittayakhom school as followings: 2.1) The organization: The learning environment should be developed to facilitate learning together and individual learning, 2.2) Strategic Planning: The school should be seek, build, develop, utilize knowledge and innovation, 2.3) Focus on Learners: The school should be have a sustainable development concept and make long-term commitment to the students, 2.4) Analytical Measurement and knowledge administrator: The school should be focusing on the educational of the learners, needs and features of future learners, 2.5) The Staffing: The school should be set the direction, school vision that focusing on students’ quality, communication direction and vision to management, 2.6) Focus on Operations: The school should be planned, using information and integrated to achieve school outcomes, 2.7) The Outcomes: Should be set indicators to improve the educational and service process.