The utility model discloses a dredger power grid harmonic monitoring device. The dredger power grid harmonic monitoring device comprises a monitoring bench, a PMU measurer, a data processor, a display, a memory, a first current transformer, and a second current transformer, the monitoring bench is provided with a display installing port and a first instrument installing port, the PMU measurer is arranged in the instrument installing port and comprises a line voltage measuring circuit, a line current measuring circuit, and an RS-485 positive and negative wiring port, a voltage acquisition port of the line voltage measuring circuit is respectively connected with a three-phase power grid, a current acquisition port of the line current measuring circuit is respectively connected with secondary sides of the two current transformers, the PMU measurer is connected with the data processor via the RS-485 positive and negative wiring port, the display is connected with the data processor, and the memory is connected with the data processor. According to the dredger power grid harmonic monitoring device, the measurement and display of line voltages, line currents, and harmonic waves of the power grid can be realized, the measuring precision is high, the measuring instrument is integrated, and the monitoring is facilitated.