The core technology involved includes expert knowledge representation, model organization, software data exchange standard and integration of GIS, expert knowledge and analysis model. With this approach and the basic principle of the traditional digital agriculture, it is possible to tap the variable-rate water and fertilizer application to agronomic fields even in the mountainous and remote region and gain maximum benefit with minimum purchased input, which is very useful in mountainous countries with scattered and small-scale agriculture production. The framework of the developed system is a hybrid structure model composed of B/S(Browser/Server) and C/S (Client/Server), which not only extends the capability of
decision support service space but also makes the system easy to maintain. A case study is done in Guangzhou city, located in intertropical belt in the South of China and covered by mountainous landform, and shows an exciting result