Abstract-The measurement unit has a direct influence on effectiveness and accuracy for phasor measurement unit's measurement result. The article design a measurement unit of phasor measurement unit by use the DSP chip as main processor. The unit adopt DFT phasor measurement algorithm. By design the hardware circuit and software realization, the unit can import electric signal directly, and every primitive period send three phasor's positive sequence、negative sequence、zero sequence to the upper data processing center by DSP's SPI. By test, the unit can realize real-time measuring the line phasors, it has a high quality measurement accuracy, and it can follow the tacks of frequency accurately, meet the requirement for the power system stablization monitor and control.