This study undertakes a critical survey of literatures on the nest development in agricultural extension system; T&V(Traininig and Visit Extension), FSR&E(Fanning Systems Research and Extension), and FF(Farmer First). The study compares the three extension systems in their establishment, objectives, charactersistics, and methods. to find the minor factors for the betterment of agricultural extension system. Those are; 1) client-oriented program, 2) educational service, 3) comprehensive goal and work, 4) benefit to wide range of customers, 5) democratic program, 6) participatory approach, 7) four based experiment, 8) linkages among participants, 9) specialization of extensionists, 10) autonomy of extension offices, 11) humanstic program.