Abstract: The existing data communication based on RS-485 bus has shortcomings of low efficiency，low reliability，not flexible in application and higher post-maintenance cost.It is hard to meet the requirements of strong anti-interference，many nodes，long distance transmission in tailings reservoir engineering monitoring.In order to solve the deficiencies of tailing reservoir online monitoring system based on RS-485 bus in the aspect of data collection and transmission，the basic characteristics of RS-485 bus with CAN bus are contrasted，and the proposal for the CAN bus be used for the early-warning monitoring system communicate with monitoring equipment in the tailings reservoir engineering is put forward.Based on this，the tailings reservoir on-line monitoring and early warning systems based on CAN bus is established，and the monitoring system compositions and the basic functions of monitoring software are introduced.In practical engineering application，the saturation line monitoring system is established to monitor water level in each cross section of the tailings reservoir.Through the analysis of the monitoring system operation and the monitoring data of saturation line，it is shown that the system based on CAN bus is reasonable in design，which can effectively monitor the underground water level of tailings reservoir.Its real-time and reliable operation can meet the requirement of on-line monitoring in harsh environment.It has a certain application value in tailings security monitoring.

Key words: CAN bus, RS-485 bus, Tailings reservoir, Monitoring system