Abstract: The disclosure provides a system for electromagnetic monitoring of active cracks in a concrete dam. The system includes at least four electromagnetic signal acquisition devices and a main control module. Each electromagnetic signal acquisition device includes: an electromagnetic monitoring sensor, an electromagnetic signal acquisition module, a power supply module and a first wireless communication module, for collecting and extracting electromagnetic radiation signals generated by the active cracks in the concrete dam. The main control module includes: a second wireless communication module, a CPU, a data storage unit and a data display unit, for processing the electromagnetic radiation signals received by the second wireless communication module, positioning locations of the active cracks and quantifying sizes of the active cracks.