The utility model provides a multi-loop electric energy quality on-line monitoring device based on an ARM and a DSP. The multi-loop electric energy quality on-line monitoring device comprises one or more measuring modules, an ARM module, and a power supply module. The measuring modules are used for sampling signals of a power grid and calculating and processing relevant data about the electric energy quality. The ARM module, connected with the measuring modules, serves as a control core of the on-line monitoring device, controls data interaction between the measuring modules and the ARM module, and provides external communication interface. The power supply module is used for providing power to the measuring modules and the ARM module. Each measuring module includes three pairs of voltage transformers and current transformers, and is used for simultaneously monitoring three-phase voltage and three-phase current. The output end of each voltage transformer and the output end of each current transformer are connected with an AD conversion module. The AD conversion module is connected with a DSP module. The output end of each voltage transformer is also connected with the DSP module via a phase-locked loop. The DSP module is connected with the ARM module. The multi-loop electric energy quality on-line monitoring device can continuously monitor and analyze multiple monitored points at the same time, and has a remote data transmission function.