Abstract: At present, the dam safety monitoring data can't be analysed and evaluated in time in China. The Safety Monitoring Data Analysing and Evaluating System for Earth and Rochfill Dams (EDMDAS) is the device we have developed to solve this problem. It can analyse and evaluate the monitoring data of settlement, horizontal displacement, standpipe water level, piezometer water level, seepage, and round crack, giving analysis results of each point. As a result, it can exert the monitoring data's role in dam safety monitoring sufficiently, and improve dam safety management. This paper introduces the development of this device.