The invention provides a DSP-based electric energy quality online monitor. The DSP-based electric energy quality online monitor has various kinds of functions such as self diagnosis, fault recording and data communication, can provide convenience for fault analysis and has high reliability. The monitor comprises a power source a well as a sampling module, a signal processing module, a CPU module and a display and storage module which are connected with one another sequentially; the power source module is connected with the signal processing module and the CPU module; the CPU module includes a DSP chip, an analog-digital conversion and a data register unit; the signal processing module comprises an ARM processor and an active low-pass filter; peripheral circuits can be greatly decreased, and efficient integration can be realized. The DSP-based electric energy quality online monitor of the invention integrates measurement, monitoring and protection functions and can be networked to a computer through a communication interface so as to form an intelligent monitoring protection and information management system; and the DSP-based electric energy quality online monitor has a high industrial use value.