Abstract: Combined with the actual of Guangdong Province, for meeting the actual needs of application and promotion of soil testing and formulated fertilizer project, the automatic control system for soil testing and formulated fertilizer taking county as a unit was developed, using existing soil geographic information data, fertilizer data, crop fertilization model and information technology, by ArcGIS Engine component technology and Modbus RTU communication protocol. Preliminary results showed that the control system can effectively manage the soil data and geospatial data in soil testing and formulated fertilizer project, achieve the crop fertilizer and fertilizer recommendation for precise guidance at the county level, and can complete the fertilizer formula to meet the individual needs of farmers on site. K