The invention provides an earth and rockfill dam time-domain electric field monitoring system and a precise imaging method, and belongs to the technical field of real-time monitoring of earth and rockfill dam leakage safety problems. The monitoring system comprises a communication cable, a drilling cable, a drilling electrode, an integrated electrical method host, a data acquisition and processingplatform and the like; earth and rockfill dam earth electricity information is transmitted to the input end of the communication cable through the drilling cable, then transmitted to the integrated electrical method host through the output end of the communication cable and finally transmitted to the data collecting and processing platform. The precise imaging method comprises data observation and data inversion imaging. According to the monitoring system, a transverse, longitudinal and time-direction three-direction dynamic observation layout is applied, a dam body multi-hole measuring linecombined observation method is combined, real-time accurate imaging of a geoelectric field can be achieved, complete coverage type monitoring of the earth and rockfill dam is facilitated, one-time arrangement is achieved, the service cycle is long, and mass data can be obtained compared with a traditional method; according to the observation system, the time shifting electrical method technology is applied to normalized monitoring of the earth and rockfill dam, and breakthrough of the monitoring and detection integrated technology can be achieved.