The goal of this study is to develop a virtual farm for educational applications. Users can play the role of a farmer by planting vegetables and raising poultry on the virtual farm to observe their growth through online learning activities. The virtual farm possesses educational and entertaining functions, and it is designed by simulating the real situations of being a farmer to enhance users' interest and motivation in learning agricultural knowledge. It also provides an alternative way for city people to experience interesting farm life. The virtual farm is highly interactive with 3D visual effects and the attractive features of distance learning, and thus it can be used as an assistant tool in elementary science education. A teaching experiment was conducted and the results showed that the virtual farm could enhance students' learning effectiveness and motivation. (Contains 8 figures and 2 tables.)